By David Alexander and Andrea Shalal
WASHINGTON, Feb 2 (Reuters) - Facing new security challenges in the Middle East and Ukraine, the Obama administration on Monday proposed a $534 billion Pentagon base budget plus $51 billion in war funds as it urged Congress to end spending cuts which it says erode U.S. military power.
In addition to the base budget and war funding requests, the administration proposed some $27 billion in defense spending at other agencies, primarily nuclear weapons work by the Department of Energy.
The Pentagon base budget proposal broke through the $499 billion federal spending cap for fiscal year 2016, setting up a debate in Congress over whether to continue deep cuts to federal discretionary spending or to amend the limits set in a 2011 law that sought to narrow the U.S. budget deficit.
"The geopolitical events of the past year only reinforce the need to resource DoD (Department of Defense) at the president's requested funding level as opposed to current law," the Pentagon said in a statement.
The budget follows several years of deep spending cuts, also known as sequestration, included in a 2011 law meant to slash government deficits. Projected defense spending was supposed to be reduced by about a trillion dollars over a decade but defense officials say the cuts are eroding military capabilities after 15 years of war.
"As the budget makes clear, a return to sequester-level funding would be irresponsible and dangerous, resulting in a force too small and ill-equipped to respond to the full range of potential threats to the nation," the Pentagon said.
To counter Russian actions in Ukraine and elsewhere in Europe, the defense budget includes funding to increase military exercises and training with European partners and to increase U.S. military rotational deployments to the region.
It also includes funding to combat Islamic State militants in Iraq and Syria by providing training and assistance to Iraqi military troops and members of the Syrian opposition.
The proposed budget would enable the U.S. Army to fund an active-duty force of 475,000 soldiers, down slightly from its plan to retain 490,000 after the wars in Iraq and Afghanistan. The Pentagon has warned that if the 2011 budget limits remained in force, it would have to cut the Army to about 420,000 troops.
The Pentagon again sought approval for several reforms hotly opposed in Congress, including retirement of the A-10 "Warthog" close-air support aircraft, conducting a new round of U.S. base closures and curbing the rising cost of military pay and benefits.
(Additional reporting by Phil Stewart; editing by David Storey and G Crosse)