By Waleed Ibrahim

BAGHDAD (Reuters) - Any buildup of U.S. forces in the Gulf after their withdrawal from Iraq would be imprudent, Iran's foreign minister said on Monday, urging all nations to tread cautiously in a troubled region.

Foreign Minister Ali Akbar Salehi made the comments in Baghdad days after U.S. Secretary of State Hillary Clinton warned Iran not to try to exploit the U.S. withdrawal at the year-end.

"Now, about the U.S. planning to build up their forces in the region ... they are not following a rational and prudent approach," Salehi told a joint news conference with Iraqi Foreign Minister Hoshiyar Zebari.

"The Americans always have a deficit, unfortunately, in rationality and prudence. So what I expect is that it's about time for the Americans to be ... more prudent and wise in their approach," he said.

Washington is planning to bolster its military presence in the Gulf after it pulls out of Iraq, including negotiating to maintain a combat presence in Kuwait, and is considering deploying more warships in the area, the New York Times reported on Sunday.

Salehi said the region was entering a troubled period. "The consequences of these developments are not yet known to anybody, so one has to be cautious. Everybody has to be cautious, including the U.S.," he said.

Iraq and the United States failed after months of talks to agree on keeping U.S. troops in Iraq past the end of this year.

U.S. President Barack Obama announced he would stick to plans to pull out the remaining force, about 39,000 now, by the year-end, nearly nine years after the invasion that ousted Saddam Hussein.

U.S. officials have accused Iran of interfering in Iraqi affairs by supporting Shi'ite militias in Iraq.

On Sunday Iran's supreme leader Ayatollah Ali Khamenei hailed the coming withdrawal of U.S. troops from neighboring Iraq as a "golden page in that country's history.

"Iraq does not need anybody to meddle in its internal affairs. Iraq is an independent country," Salehi said.

Asked if Iran was ready to make a deal with Iraq to train its forces and exchange intelligence information, Salehi said: "Sure. (There is) no problem in such a suggestion, to make a thorough pact that includes all these (ideas)," he said.

(Editing by Jim Loney)