The United States on Monday urged Iran to be cooperative when a team from the International Atomic Energy Agency (IAEA) visits Iran later this month to discuss issues related to its controversial nuclear program.

"Well, obviously, we call on Iran to cooperate fully with the IAEA on this trip," the State Department spokeswoman Victoria Nuland said at a regular news briefing.

"The IAEA is going in a constructive spirit, and it's asking Iran to display the same attitude," she said, adding that "There is a lot of work to do."

The European Union (EU) decided earlier Monday to target Iran's oil exports and central bank for sanctions, banning imports of Iranian crude oil and petroleum products.

The move follows new U.S. sanctions authorized by U.S. President Barack Obama at the end of 2011, under which foreign firms continuing to do business with Iran's central bank and financial sector are shut out from America's financial market.

The IAEA's team, led by its deputy director Herman Nackaerts, will visit Iran on Jan. 29-31 with a view to "resolving all outstanding substantive issues," as the UN nuclear watchdog put it.

A Nov. report by the agency pointed to clandestine activities towards bomb making in Iran, though the Islamic republic insists its nuclear program is only for peaceful purpose.

Nuland said that the report raised "a huge number of" questions, and the IAEA team will be seeking answers to them.

"It's incumbent on Iran to be supportive," she said. "Obviously, the proof will be in the pudding. We'll have to see whether the IAEA gets into the sites it wants to see, gets the information that it wants to have."