Gen Odierno said Iran was using its contacts among Iraqi politicians
The commander of US military forces in Iraq has accused Iran of trying to bribe Iraqi legislators into rejecting a security deal with the US.
Gen Ray Odierno told the Washington Post that many intelligence reports suggested "pay offs" were being made, but that he had no definitive proof.
The US and Iraq governments are negotiating a security pact to allow US forces to stay beyond the end of 2008.
Iraq's parliament must ratify the agreement for it to take effect.
American and Iraqi officials have said they are close to finalising the long-awaited agreement before the expiry of a UN Security Council resolution that sanctioned the US troop presence in Iraq.
One of the most sensitive issues is over immunity for US troops who break Iraqi law.
Gen Odierno said Iran was utilising its contacts with the many Shia Iraqi politicians who took refuge in Iran when Saddam Hussein was in power to try to influence the Iraqi parliament's eventual vote on the deal.
"We know that there are many relationships with people here for many years going back to when Saddam was in charge, and I think they're utilising those contacts to attempt to influence the outcome of the potential vote in the council of representatives," he said in an interview with the Washington Post.
"We get reports of people coming in to pay off people to vote against it. Whether it's true or not I have no specific proof, but there are many intelligence reports that say that activity is going on."
The US has previously said that Tehran is providing training and weapons - including advanced roadside bombs - to Iraqi insurgents.
Iran has denied the accusations and says that US troops in Iraq are the cause of instability there.