Iran's foreign minister delivered a blunt challenge to the United States on Saturday, saying Tehran is willing to help U.S. troops withdraw from neighboring Iraq but only if Washington makes some tough policy changes.

Foreign Minister Manouchehr Mottaki claimed U.S. troops were responsible for at least half the violence tearing apart Iraq and that their departure would pay security dividends for the entire region.

"If the United States changes its attitude, the Islamic Republic of Iran is ready to help with the withdrawal from Iraq," Mottaki told the International Institute of Strategic Studies conference here. "Fifty percent of the problem of insecurity in Iraq is the presence of foreign troops."

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Mottaki echoed calls made last week by Iran's top national security official, Ali Larijani, for Gulf Arab countries to eject American bases in their countries and establish a regional security pact with Iran. Mottaki went further and offered deeper cooperation with the six Gulf Arab states on energy, tourism, business and counter-narcotics.

Iran's offers do not seem to have tempted Gulf neighbors who are apparently more worried about the dangers of living near Iran's nuclear facilities, especially amid threats by Washington and Israel to use military force to destroy them.

Mottaki's forceful speech was a challenge to U.S. interests in the Gulf and a strong display of the country's rising assertiveness in the face of U.S failures in the region.

At one point, Mottaki addressed an international audience that included U.S. Vice Adm. David Nichols, the deputy chief of U.S. Central Command, and said the regional chaos sparked by the Bush administration's twin wars demonstrated that U.S. military force was no longer a realistic policy option in the Middle East.

"Today the time of threats is over. The period of unilateralism is over," Mottaki said. "Look at Iraq. Look at Afghanistan. That gives us a very important lesson."

Iran's proposal for a Gulf security alliance shows no sign of gaining traction among the region's Arab leaders. Bahraini Foreign Minister Sheik Khalid bin Ahmed Al Khalifa said security of the energy-rich region depends on the United States, the European Union and other major oil-importing countries.

Much of the discussion at this security conference centered on the U.S. Iraq Study Group report, and its recommendation that Washington seek Iran's help in steering Iraq away from civil war.

William Cohen, defense secretary under President Clinton, urged Iran to push for talks with Washington.

"If you forgo aspirations for nuclear weapons and cut off funding for radical elements and support the Mideast peace process, then yes, you'd be welcomed into the international community. We'd have billions of dollars going into your economy," Cohen told the Iranians among 250 delegates from 22 countries.

"If Iran is simply interested in pursuing a nuclear energy program and not weapons, that's something the U.S. wouldn't object to and would support."

For more news, go to FOXNews.com's Iraq Center.