US President Barack Obama has ordered the freezing of Iran's property under American jurisdiction, including that of the country's central bank, the White House said.

The US and its allies are pressing hard over Tehran's controversial nuclear programme. Terming them "additional steps" against Iran, Obama ordered all property and interests in property of the government of Iran as well as the republic's financial institutions under US jurisdiction including the Central Bank of Iran, to be "blocked and may not be transferred, paid, exported, withdrawn, or otherwise dealt in", Xinhua quoted a statement as saying.

The property of people determined to have links with those already under US sanctions was ordered to be frozen as well. Obama said the move aimed to counter the "deceptive practices" of Iran's central bank to conceal transactions of sanctioned parties, the deficiencies in Iran's anti-money laundering regime and the weaknesses in its implementation, and the "continuing and unacceptable" risk posed to the international financial system by Iran's activities.

Obama's order, which became effective Monday, came amid heightened tensions between Western countries and Iran over the latter's nuclear programme and growing rumours about an imminent strike by Israel on Iran's nuclear facilities.

White House spokesman Jay Carney called the action one "reflective of the policy that we've taken for quite a long time now in reaction to Iranian behaviour". In an interview with the NBC television network, Obama said the US will work with Israel to prevent Iran from becoming a nuclear power, and urged Iran to "stand down" on the current standoff.

The US and its European allies have expanded their sanctions against Iran to target its oil exports, prompting threats by Tehran to close the Strait of Hormuz, one of the world's most critical oil routes.