KUALA LUMPUR, Feb 15 (Reuters) - Iraq assured Islamic nations on Thursday that a new U.S.-backed security plan now under way will help end sectarian violence and sought their assistance to rebuild the war-torn nation.

Iraq has closed its borders with Iran and Syria as U.S. and Iraqi troops tightened their grip on Baghdad on Thursday, setting up more checkpoints that stopped and searched even official convoys for weapons.

"There are strong guarantees the (security) steps will be successful," Khaled al-Attiya, a deputy speaker of Iraq's parliament, told Reuters at an annual meeting of lawmakers from the 57-nation Organisation of Islamic Conference (OIC).

"The plan will give the Iraqi government enough authority to take control," said Attiya, a senior leader from the dominant Shi'ite bloc.

"It will be followed by economic and political action to strengthen security, stability and reduce ethnic tensions," he said after a meeting with Malaysia's Deputy Prime Minister Najib Razak.

Malaysia, the current chair of the OIC, had opposed the U.S.-led occupation of Iraq. But Kuala Lumpur has said it was keen to participate in the rebuilding of the country.

The border closures came as thousands of U.S. and Iraqi troops stepped up an offensive in Baghdad, the epicentre of sectarian violence between minority Sunnis and majority Shi'ites that has pitched the country toward all-out civil war.

U.S. officials have long accused Syria of allowing foreign fighters to cross its long, porous border into Iraq, and at the weekend presented evidence of what they said was Iranian-made weapons being smuggled into Iraq.

Shi'ite officials have warned that failure could mean a collapse of the Shi'ite-led government. U.S. President George W. Bush is sending more than 17,000 additional troops for the crackdown.

Attiya said he welcomed any offers from Malaysia and other rich OIC nations to reconstruct his country and revive the battered economy.

"They can invest in Iraq and this will definitely reduce the jobless rate to bring prosperity. This will reduce the tension in Iraq," he said.

AlertNet news is provided by