Iran warned Saudi Arabia on Tuesday to rethink an offer to make up for oil lost to world markets as a result of threatened curbs on its exports as diplomats said an EU embargo may be in force by July.

Foreign Minister Ali Akbar Salehi urged Riyadh to "reflect" on its pledge to use its spare capacity to compensate for any reduction in Iran's oil sales that results from US-led efforts to tighten sanctions over the Islamic republic's controversial nuclear programme.

Salehi said the Saudi offer was "not friendly."

In a boost to Iran's efforts to protect its key oil sector, its second biggest client, India, said it had no plans to curtail purchases in response to the US-led campaign.

"We continue to buy oil from Iran," Indian Foreign Secretary Ranjan Mathai said in New Delhi.

"We have accepted sanctions which were made by the United Nations. Other sanctions do not apply to individual countries," he added in reference to unilateral sanctions adopted by the European Union and the United States.

Energy hungry India is Iran's second largest client after China, and absorbs about 20 percent of its crude exports, buying about 400,000 barrels per day at an annual cost of around $12 billion (9.4 billion euros).

Meanwhile, ahead of a key meeting on Monday, diplomats in Brussels said the European Union could have an embargo on Iranian oil imports in force by July as a compromise took shape between champions of tougher sanctions and member states that rely heavily on purchases from Iran.

"A deal should be finalised in the coming days," one diplomat said. "A consensus is taking shape over the transitionary phase," said another.

There had been been disagreement within the 27-nation bloc, which takes in some 450,000 barrels per day of Iranian oil, about the grace period that should be allowed for the ban to be phased in.

Some member states wanted an earlier, three-month deadline, whereas financially stressed nations that rely on Iranian crude -- notably Greece, Italy and Spain -- wanted up to a year.

Iranian oil accounted for 34.2 percent of Greece's imports, 14.9 percent of Spain's and 12.4 percent of Italy's in the first nine months of last year, according to the latest EU figures.

Washington has been spearheading a campaign to squeeze Iran's oil exports to put greater pressure on its nuclear programme, which Western governments fear is cover for a drive for a weapons capability, an ambition Tehran denies.

President Barack Obama recently signed a bill allowing penalties on foreign banks who settle oil import costs with Iran's central bank.

Last week, US ally Japan appeared to backtrack on a pledge to cut its imports from Iran, while China has refused to bow to US pressure.

Iran has not only been battling mounting US-led pressure on its economy, but also a covert campaign, including murder and sabotage, which it has blamed on Israel and the United States, despite Washington's denials and Israel's silence.

President Mahmoud Ahmadinejad ordered security stepped up for all of Iran's nuclear scientists following the assassination last week of Mostafa Ahmadi Roshan, the 32-year-old deputy director of a key facility.

"Whoever is active in the nuclear field will be put under special care," official media quoted First Vice President Mohammad Reza Rahimi as saying.

Iran has said it is willing to restart talks with world powers on its nuclear activities that collapsed a year ago, but it has not formally responded to an EU letter offering a resumption of the negotiations.

A high-level delegation from the UN nuclear watchdog, the International Atomic Energy Agency, is to visit Iran from January 29 to 31, the Fars news agency reported.

Iran's envoy to the watchdog, Ali Ashgar Soltanieh, said the visit was "a new sign of the transparency in Iran's nuclear programme and activities and in our interaction with the International Atomic Energy Agency," Fars added.

But a defiant Iran has also raised new Western concerns in recent weeks by starting uranium enrichment operations at a heavily defended bunker southwest of Tehran, and by announcing fresh naval exercises in the Strait of Hormuz, a strategic choke point for much of the Middle East's oil.

burs/kir/al