Sen. Barack Obama (D-Ill.), who wrapped his party’s presidential nomination just this week, is already besieged by liberal constituencies demanding that he cut military spending to boost  social programs.

Two influential liberal groups have sent the presumptive Democratic nominee a letter pressing him to support cuts to defense programs to pay for universal preschool, relief for Americans facing foreclosure on their homes and expanded benefits for military veterans.

Their calls for defense cuts have drawn the support of leading House liberals, many of whom gave Obama crucial support early in his contest against Sen. Hillary Rodham Clinton (D-N.Y.).

The groups have also called on presumptive Republican nominee Sen. John McCain (Ariz.) to support the cuts. There is less pressure on McCain, however, because fellow Republicans have kept quiet on the issue. McCain also expects little support from black voters.

But McCain could feel some discomfort because his campaign views Hispanics as a crucial voting bloc. His support for shifting emphasis from defense to social programs could help him appeal to that group. The calls of liberal groups and lawmakers come at a particularly awkward time for Obama.

Since clinching the party’s nomination on Tuesday, Obama has already tacked to the right on security issues in preparation for the general election. During a speech to the American Israel Public Affairs Committee Wednesday, Obama proposed sanctions on Iran that analysts viewed as far tougher than what he suggested before.

Now Obama must balance tough talk on national security with the desires of many Democrats to slim American military power.

Liberal groups and lawmakers have targeted the Department of Defense’s largest acquisition program: the Joint Strike Fighter program, which will provide more than 2,000 aircraft to the Navy, Marines and Air Force.

The Black Leadership Forum and LULAC wrote that cutting the program “would free up $1 trillion in the federal budget.”

“America could fund years of universal healthcare at $120 [billion] a year; we could fund universal preschool with $35 billion.”

Rep. Barbara Lee (D-Calif.), co-chairwoman of the Congressional Progressive Caucus, said the rapid growth of defense spending compared to domestic spending in recent years is “outrageous.” She wants to slim defense programs and boost education and healthcare funding.

Lee and other House liberals would like to see about $60 billion in defense spending cuts. Specifically, they want to steer money away from what they call “Cold War-era” weapons systems, such as the F-35 Joint Strike Fighter. Liberals have also called for cuts to the ballistic missile defense program, the F/A-22 Raptor, the V-22 Osprey and the DDG 1000 Zumwalt Class Destroyer.

“This is one of many issues the caucus will be talking about to him,” Lee said of plans to press Obama on defense budget cuts. “I’m definitely going to present this.”

Obama’s campaign did not respond to a request for comment.