* Obama pledges "last" supplemental request
* Aid for Mexico, Guantanamo shutdown also included (Updates with Obama, adds Gates and members of Congress)
By Andrew Gray
WASHINGTON, April 9 President Barack Obama asked the U.S Congress on Thursday for an extra $83.4 billion to fund the wars in Iraq and Afghanistan this year, citing threats from al Qaeda and a resurgent Taliban.
The request, to cover the rest of the 2009 fiscal year which ends on Sept. 30, comes on top of more than $822 billion that Congress has approved to fund the wars since September 2001, Obama said.
"We face a security situation in Afghanistan and Pakistan that demands urgent attention," he said in a letter to Nancy Pelosi, speaker of the House of Representatives, urging lawmakers to approve his request swiftly.
"The Taliban is resurgent and al Qaeda threatens America from its safe haven along the Afghan-Pakistan border."
Almost 95 percent of the funding would go to support military efforts to stabilize Iraq, Afghanistan and Pakistan, Obama said in the letter released by the White House.
The request also includes funding for other national security priorities of the administration, including assistance for anti-drug efforts in Mexico, security assistance in Lebanon and closing down the Guantanamo Bay prison.
Congress has already approved $65.9 billion for the wars in 2009 and some anti-war Democrats expressed reservations about the new request.
But Defense Secretary Robert Gates said Obama's policies on Iraq and Afghanistan enjoyed broad support on Capitol Hill.
"The alternative to the supplemental is a sudden and precipitous withdrawal ... from both places. And I don't know anybody who thinks that's a good idea," Gates said.
OBAMA PLANS END TO SUPPLEMENTALS
The administration of former President George W. Bush was widely criticized for using such supplemental requests to fund the wars. Both Democrats and Republicans said such urgent requests faced less scrutiny than the regular budget.
Obama has pledged to put an end to the practice and he said Thursday's request was "the last planned supplemental".
The White House said it had to submit another large supplemental request this time because the wars were only half-funded for the rest of the 2009 fiscal year.
"The honest budget and appropriations process that the president has talked about falls somewhat victim to the fact that this is the way that wars have been funded previously," White House spokesman Robert Gibbs told a news briefing.
Representative Jim McGovern, a Democrat, said he was very worried about by Obama's plan to send tens of thousands more troops to Afghanistan, and was not a guaranteed "yes" vote for the supplemental.
"I was against the war in Iraq from the very beginning, and I don't want us to make the same mistake the second time," McGovern told Reuters.
Steny Hoyer, the leader of the Democratic majority in the House of Representatives, indicated the request would be dealt with swiftly.
"Timely consideration of the supplemental is especially important to our men and women in uniform, who depend on it for the resources they need to do their jobs," he said.
"Congress looks forward to giving it that consideration in the weeks to come," Hoyer said in a statement. (Additional reporting by Susan Cornwell, David Alexander, Jeff Mason and Jeremy Pelofsky; editing by Mohammad Zargham)