Citing Iran "contrary" to U.S. interests, President Barack Obama said Wednesday that the United States will continue sanctions set by the previous administrations on Iran.

In a letter to the Congress, Obama told lawmakers that he has decided to make the National Emergency on Iran, which will be expired on March 15, continue in effect for one year, because of Iran's threat to U.S. national interests.

The national emergency with respect to Iran has been continued for some 10 years since it was announced by the Clinton administration in March 1995, under which the United States can take a series sanctions on Tehran.

"The crisis between the United States and Iran resulting from actions and policies of the Government of Iran that led to the declaration of a national emergency on March 15, 1995, has not been resolved," said the president.

"The actions and policies of the Government of Iran are contrary to the interests of the United States in the region and pose a continuing unusual and extraordinary threat to the national security, foreign policy, and economy of the United States," he added.

"It is necessary to continue the national emergency declared with respect to Iran and maintain in force comprehensive sanctions against Iran to respond to this threat," Obama said.

The United States severed its ties with Iran in 1980, while the U.S.-Iran relationship has been further worsened since 9/11 attack with the Bush administration labeled Tehran as an axis of evil, and accused Iran of developing nuclear weapons, supporting terrorism and the radical Islamic fundamentalism.

The United States, Israel and other Western countries voice deep concerns on Iran's nuclear program, saying Tehran may obtain the uranium fuel needed for nuclear weapons by the same process to purify uranium. Iran insists its nuclear program is for peaceful purpose.

The Obama administration has been trying the so called dual-track, namely engagement and sanction, to bring the international community together to make Iranian leaders realize the "importance of changing their actions and decisions concerning their nuclear program."

In hearings at the Congress last month, Secretary of State Hillary Rodham Clinton told lawmakers that Iran's refusal to live up to its responsibility has left the international community "little choice but to impose greater costs for its provocative steps."