VIENNA, Feb 20: The United States on Monday intensified pressure on Iran by sending a second aircraft carrier to the Gulf and slapping sanctions on some Iranian banks and companies.

The British Broadcasting Corporation quoted unnamed diplomatic sources as saying contingency planning for any US attack went beyond targeting atomic sites to include most of Iran's military infrastructure.

Aircraft carrier John C. Stennis and warships in its group joined another carrier in the strategic Gulf waterway on Monday, the US Navy said.

Rear Admiral Kevin Quinn, commander of the Stennis strike group, said in a statement his ships were `here to help foster stability and security in the region’. Analysts regard the deployment as a warning to Iran to retreat from enrichment work.

The BBC said in its report of possible US action: “It is understood that any such attack -- if ordered -- would target Iranian air bases, naval bases, missile facilities and command-and-control centres.”

Nuclear targets would include the uranium enrichment facility of Natanz in central Iran where Tehran operates a few hundred centrifuges at a research level, but plans to install thousands to achieve so-called `industrial-scale’ enrichment.

Mohamed ElBaradei, the IAEA chief, said in a Financial Times interview on Tuesday that Iran would be able to install 3,000 centrifuges as the basis for industrial scale fuel production in six to 12 months.

Diplomats monitoring IAEA inspections have said Tehran has set up several cascades (interlinked networks) of 164 centrifuges each in the plant and is poised to activate them to feed in uranium for refinement into fuel at any time.

One diplomat said a nine-tonne container of uranium hexafluoride gas, the feedstock for nuclear fuel, had been lowered into the plant in recent days.

Mr ElBaradei noted intelligence estimates that Iran remains four to eight years away from mastering the means to assemble an atom bomb, assuming it wanted one, and that meant ample time remained for talks. Sanctions alone would not work, he said.

TALKS WITH IAEA: Ali Larijani, Iran’s chief nuclear negotiator, was in Vienna on Tuesday to meet the head of the International Atomic Energy Agency (IAEA) on the eve of a United Nations deadline for it to back down on a programme the West suspects aims to develop nuclear weapons.