Trump seeks 'historic' U.S. military spending boost, domestic cuts

* Trump calls for rise in spending for "depleted military"

* Actual increase would be only slightly above inflation

* Plan foresees cuts to key domestic programs (Recasts, adds increases over actual spending, McCain statement)

By Steve Holland

WASHINGTON, Feb 27 (Reuters) - President Donald Trump is seeking what he called a "historic" increase in defense spending, but ran into immediate opposition from Republicans in Congress who must approve his plan and said it was not enough to meet the military's needs.

The proposed rise in the Pentagon budget to $603 billion comes as the United States has wound down major wars in Iraq and Afghanistan and remains the world's strongest military power.

The plan came under fire from Democratic lawmakers, who said cuts being proposed to pay for the additional military spending would cripple important domestic programs such as environmental protection and education.

A White House budget official, who outlined the plan on a conference call with reporters, said the administration would propose "increasing defense by $54 billion or 10 percent." That represents the magnitude of the increase over budget caps Congress put in place in 2011.

But Mick Mulvaney, the White House budget director, said the plan would bring the Pentagon's budget to $603 billion in total, just 3 percent more than the $584 billion the agency spent in the most recent fiscal year, which ended on Sept. 30, 2016.

The rise would be slightly higher than the country's current 2.5 percent rate of inflation.

"President Trump intends to submit a defense budget that is a mere 3 percent above President (Barack) Obama’s defense budget, which has left our military underfunded, undersized, and unready to confront threats to our national security," John McCain, the Republican chairman of the Senate Armed Services Committee, said in a statement.

The defense boost would be balanced by slashing the same amount from non-defense spending, including a large reduction in foreign aid, the White House budget official said.

Trump does not have the final say on federal spending. His plan for the military is part of a budget proposal to Congress, which, although it is controlled by his fellow Republicans, will not necessarily follow his plans. Budget negotiations with lawmakers can take months.

McCain told reporters he would not vote for a budget with the slight military increase and thought it would face opposition in the Senate.

Trump told state governors at the White House his budget plan included a "historic increase in defense spending to rebuild the depleted military of the United States of America."