The US Senate Banking Committee approved a controversial measure Thursday that would ratchet up sanctions on Iran, a legislative weapon Congress could wield after March if international nuclear talks hit an impasse.

Senators voted 18 to 4 to advance the so-called Kirk-Menendez bill, which is steadfastly opposed by the White House.

"It is clear that further action is necessary to compel Iran to reach an acceptable agreement, which is why I strongly support this critical bill," committee chairman Senator Richard Shelby said after the vote.

President Barack Obama's administration is hostile to any congressional action that might scupper the ongoing landmark negotiations between international powers -- the United States, Russia, China, Britain, France and Germany -- and Iran.

Negotiators are eyeing the end of March for a political agreement, and June 30 as the deadline for a final pact which Washington hopes will prevent Iran from developing a nuclear weapon.

Some US lawmakers insist on keeping Iranian leaders' feet to the fire by pressing ahead with a deferred sanctions bill before June 30, which would trigger a gradual escalation of economic sanctions beginning in July should talks collapse or if Tehran violates its obligations.

But in a victory for Obama, senators on Tuesday agreed to delay a full Senate vote until at least March 24 to allow international negotiators to reach a political framework agreement without congressional pressure.

In order to be ready to launch such a debate on the Senate floor after that date, the Banking Committee finalized the bill's text Thursday, a procedural requirement that served to revive the threat of new sanctions.

Currently, 35 of the Senate's 100 members officially back the bill, a figure that is expected to increase in coming months.

On Tuesday, ambassadors from France, Britain, Germany and the European Union met in Washington with Senate Democrats urging them to ease the pressure.

"Let's give time to the nego(tiations)," French ambassador Gerard Araud posted on Twitter, recalling that while the March 24 date was a "goal," the true deadline for an agreement remained June 30.

If Congress passes the final Kirk-Menendez bill, Obama is expected to veto it.

Dead Argentine prosecutor wary even of his guards: aide
Buenos Aires (AFP) Jan 29, 2015 - The prosecutor whose suspicious death set off a crisis for Argentina President Cristina Kirchner no longer trusted even his bodyguards at the violent end of his life, an assistant said Wednesday.

A tense Diego Lagomarsino, his voice breaking at times, recounted at a news conference in Buenos Aires how Alberto Nisman had pleaded to be given the .22-caliber revolver that was used to put a bullet through his head. Who pulled the trigger is not clear.

Nisman's security chief has been suspended and is under investigation along with two other members of his guard detail, a court source said.

The 51-year-old special prosecutor was found dead at his home January 18, a day before he was to go before a congressional committee to make a bombshell accusation: that Kirchner shielded Iranian officials implicated in the 1994 bombing of a Jewish charities office, known as AMIA.

Lagomarsino, a computer expert and the last person known to have seen Nisman alive, said the prosecutor was desperate for the gun, saying: "I no longer trust even my guards."

"He told me that he was not going to use the weapon," Lagomarsino said.

The car-bombing of the AMIA was the worst terror strike on Argentine soil in modern history and remains a wound in the collective history of Argentina's Jewish community, Latin America's largest.

No prosecution has been completed in the case, two decades on; 85 people were killed and 300 injured.

Kirchner denies the claims prepared by Nisman, and alleges that his death -- which initially was suspected suicide -- was a plot to discredit her, suggesting Nisman was manipulated by former intelligence agents who then killed him to smear her.

Nisman contended that the government had agreed to swap grain for oil with Tehran in exchange for withdrawing "red notices" to Interpol seeking the arrests of the former and current Iranian officials accused in the bombing.

- Pleading for pistol -

According to Lagomarsino, Nisman told him that -- as well as his own safety -- he also feared for that of his two daughters, who are seven and 15 years old and were on vacation in Spain at the time.

"Do you know what it is like that your daughters don't want to be with you because they are afraid something will happen to them?" Lagomarsino quoted Nisman as saying.

Lagomarsino, who had been reluctant to hand it over, said Nisman badly wanted the gun to "carry it in the glove compartment in case some crazy person came by shouting, 'You traitor!' This was a weapon that was truly on its last legs."

After Nisman's death, Lagomarsino was charged with giving a firearm to someone other than its registered owner. He is the only person to be charged so far in the murky case.

He was at the news conference with his lawyer, Maximiliano Rusconi, who said earlier he would ask that Kirchner be called to testify in his client's case.

- 'We are all Nisman' -

On Monday, Kirchner, 61, announced plans to disband Argentina's Intelligence Office and replace it with a new federal intelligence agency.

Investigators initially said they believed Nisman committed suicide, but classified his death as "suspicious" and said they have not ruled out murder or an "induced suicide."

Ruben Benitez, a Nisman confidant who has been suspended, coordinated a security team of 10 officers who protected the prosecutor.

According to a leaked statement made to the investigation's head prosecutor, Benitez said he advised Nisman against buying a gun just days before his death.

But the suspended officers have come under scrutiny for contradictory statements to the investigating prosecutor, Viviana Fein.

Nisman was mourned at a small family-only ceremony Wednesday at a Jewish cemetery on the outskirts of Buenos Aires. Some demonstrators showed their respects outside waving signs reading "Cristina = Killer" and "We are all Nisman."

Kirchner was planning to travel to key economic partner China on Saturday despite the maelstrom.

Iran, Europe negotiators to meet Thursday in Istanbul
Tehran (AFP) Jan 28, 2015 - Iranian officials will meet with European members of the P5+1 group in Istanbul on Thursday under the ongoing diplomatic effort to secure a deal over Tehran's disputed nuclear programme.

The meeting with British, French and German diplomats was announced by Iran's foreign ministry spokeswoman Marzieh Afkham during a weekly press briefing in Tehran.

The EU, which has chaired the P5+1 talks, said separately that its political director Helga Schmid would also attend.

However, a senior State Department official said there were no plans for the United States to participate in the Istanbul talks which he said were part of the bilateral discussions between Iran and the EU.

Under an interim agreement, representatives of the P5+1 (United States, Russia, China, Britain, France and Germany) and Iran gave themselves until March 31 to reach a political deal. The two parties are seeking a comprehensive accord by a June 30 deadline.

Two such deadlines were missed last year and both sides have admitted that big differences remain on the hard detail of what the final pact would look like.

Afkham told reporters there could be meetings with P5+1 members at a security conference in Munich next month, where Iran's Foreign Minister Mohammad Javad Zarif is already scheduled to meet US Secretary of State John Kerry.

Under an interim deal, Iran's stock of fissile material has been diluted from 20 percent enriched uranium to five percent in exchange for limited sanctions relief.

Experts say such measures pushed back the "breakout capacity" to make an atomic weapon, which Iran denies pursuing.

Tehran insists its nuclear programme is for domestic energy production and that it needs to increase its enrichment capacity to make fuel for a fleet of power reactors that it is yet to build.

World powers, however, are skeptical about why Iran needs such a large enrichment capability, and UN atomic inspectors say Tehran has not yet fully addressed questions about past nuclear activities.

Zarif meanwhile was quoted by an Iranian newspaper Wednesday as saying there was a "general agreement that Iran could have a nuclear enrichment programme, no sites will be closed and sanctions should be lifted".

"But the discussions are continuing on the level of enrichment, on when Iran will begin industrial scale enrichment and how nuclear research and development will be done," he told Etemad daily.

The future of a heavy water reactor at Arak in central Iran is also to be resolved, Zarif added.