U.S. Defense Secretary Leon Panetta engaged in a heated debate with Republican Senators on Tuesday over the decision to pull all U.S. troops out of Iraq by the end of the year, denying it was political plan aimed at aiding the re-election campaign by President Barack Obama.

At a hearing held by the Senate Armed Services Committee, Panetta refuted the claim by senior Republican Senator John McCain that the U.S. government failed to negotiate with Iraq for a limited presence of U.S. troops who could help train Iraqi troops to maintain its security and counter Iran's influence.

President Obama announced in October that the remaining 24,000 U.S. troops will return home by the end of the year, fulfilling one of his campaign promises made in 2008.

Panetta defended the decision on Iraqi pullout, blaming it for the failure by the Iraqi government to grant U.S. troops legal immunity if they continue to stay in the country. "If you're going to engage in those kind of operations, you absolutely have to have immunities," he said.

But McCain refused to accept Panetta's explanation, accusing the Obama administration of making the Iraqi pullout decision simply because it was political motivated. "The truth is that this administration was committed to the complete withdrawal of U.S. troops from Iraq, and they made it happen," he said.

"That's just simply not true," Panetta wasted no time in shooting back. "That's simply not true. This is about negotiating with a sovereign country, an independent country. This was about their needs; this is not about us telling them what we're going to do for them," he added.

The Iraqi pullout decision was made by Obama after he announced in June a plan to withdraw a third of U.S. troops from Afghanistan by the end of next summer. Republican lawmakers believed that both plans were designed by the Obama strategists as part of their efforts to get the president re-elected in the 2012 elections.

"I think it's no accident that the troops are coming home (from Afghanistan) two months before his election," Senator Lindsey Graham said at the same hearing Tuesday.

Martin Dempsey, chairman of the Joint Chiefs of Staff, confirmed that he and other senior Pentagon officials had been lobbying Iraqi leaders to accept a small permanent presence of U.S. military personnel after the U.S. pullout from the country.

Meanwhile, Dempsey assured the Senators that the U.S. will provide anti-terrorism training for Iraqi forces at about 10 camps after the U.S. troop withdrawal from Iraq.

He added that the U.S. will also have ground, air and naval forces to rotate in and out of Iraq's neighboring country of Kuwait, confirming earlier media reports that the U.S. may redeploy about 4,000 of the troops currently stationed in Iraq to Kuwait.