Iran on Friday rejected allegations by the US director of national intelligence James Clapper that the Islamic republic was more willing now to carry out attacks on American soil.

"Iran categorically denies James Clapper's unfounded allegations," foreign ministry spokesman Ramin Mehmanparast said.

"Those who are themselves accused of supporting the assassination of Iranian scientists in Tehran cannot allow themselves to make such false and inexact allegations," he said.

In written remarks on Tuesday to senators, Clapper said an alleged plot last year to assassinate the Saudi ambassador to the United States showed Tehran might be more willing now to carry out attacks on US soil.

"Iran's willingness to sponsor future attacks in the United States or against our interests abroad probably will be shaped by Tehran's evaluation of the costs it bears for the plot against (Saudi Arabia's) ambassador as well as Iranian leaders' perceptions of US threats against the regime," he said.

The United States made its allegations early last October and claimed it traced the supposed plot back to the Quds Force, a special operations unit of Iran's Revolutionary Guards.

Iran has repeatedly denied any involvement in the plot, which have strained its already frayed relations with Saudi Arabia.

A key US Senate panel on Thursday adopted a sweeping package of tough new sanctions aimed at forcing Iran to freeze its controversial nuclear programme amid escalating worries of a military confrontation.

The Senate Banking Committee approved the harsh new measures by voice vote, without dissent, as part of a mounting campaign in the US Congress to tighten the economic screws on defiant Iran.

Tehran denies Western charges that it seeks the ability to build a nuclear weapon, insisting its atomic activities are an effort to develop a civilian power-production capability.

Mostafa Ahmadi Roshan, a 32-year-old deputy director of Iran's main uranium enrichment plant, was murdered on January 11 along with his driver/bodyguard when assassins on a motorbike fixed a magnetic bomb to their car.

It was the fifth such incident targeting Iranian scientists in the past two years. Four other scientists -- three of them involved in Iran's nuclear programme -- died in the attacks.

Iranian officials say the attacks are a covert campaign by Israel and the United States.

Pentagon chief urges world unity on Iran sanctions
Ramstein Air Base, Germany (AFP) Feb 3, 2012 - The world must join together in backing tough sanctions to pressure Iran into giving up its suspect nuclear programme, US Defense Secretary Leon Panetta said Friday.

Describing the sanctions as "very tough" political and economic measures, Panetta said: "We've a tremendous amount of pressure on Iran to isolate Iran from the rest of the world.

"We've got to continue that kind of pressure," he said, in response to question from a US trooper during a visit to the US air base of Ramstein in the German state of Rheinland-Pfalz.

"My view is that right now the most important thing is to keep the international community unified in keeping that pressure on to try to convince Iran that they shouldn't develop a nuclear weapon..." Panetta said.

"If they don't, we have all options on the table," he said.

Panetta's comments came a day after Israel launched new threats of military intervention. There is heightened speculation that Israel is contemplating air strikes against Iranian nuclear facilities, with or without US help.

The Jewish state has pushed for tough sanctions and warned it retains the option of a military strike if necessary to prevent Tehran from obtaining atomic weapons.

Israel has the Middle East's sole if undeclared nuclear arsenal, which international experts believe contains between 100 and 300 nuclear warheads, but it has never confirmed or denied such reports.

Israeli Defence Minister Ehud Barak on Thursday praised new European sanctions against Iran's oil sector, being phased in over the next five months, and called to extend them to the financial system and central bank.

Later Barak said there was currently "broad international understanding that if the sanctions do not achieve their desired goal of stopping the Iranian nuclear military programme, the need to consider action will arise."

He also stressed the need for timely "action" against Iran, without specifying its nature.

Western economic sanctions have ramped up against Iran over the past three months, since the UN nuclear watchdog issued a report saying it had evidence the Islamic republic appeared to be researching atomic warheads.

A key US Senate panel adopted a sweeping package of tough new sanctions Thursday targeting Iran's national oil and tanker firms and its elite Islamic Revolutionary Guards Corps.

It would for the first time also widen sanctions on Iran's energy sector to any joint venture anywhere in the world where Iran's government is a substantial partner or investor.