WASHINGTON, March 11 (NNN-KUNA) -- US President Barack Obama has extended an executive order declaring a national emergency against Iran, the White House said.

Executive Order 12,957, originally signed in March 1995 and due to expire next week, declares a national emergency against Iran to deal with "unusual and extraordinary threat to the national security, foreign policy, and economy of the US by the government of Iran."

In a statement released by the White House Wednesday, Obama said he would continue the national emergency for one year, "because the actions and policies of the Government of Iran continue to pose an unusual and extraordinary threat" to the US.

The executive order comes as fuel sanctions against Iran intensify. International oil companies Royal Dutch Shell, Glencore, and Vitol have announced they will no longer sell oil to Iran in a bid to deter Iran's nuclear ambitions.

While Iran remains one of the world's largest oil exporters, it still relies on imports for about 40 per cent of its refined product.

US lawmakers are working on legislation that backs unilateral sanctions on companies that make fuel deals with Iran.

-- NNN-KUNA