The Senate rejected a proposal to take some money from President Bush's proposed missile defense budget and spend it instead on such tasks as securing "loose nukes" (search) and America's ports and borders.

It voted 56-44 Tuesday against an amendment to the defense authorization bill (search) that would have shifted $515 million away from the proposed $10.2 billion missile defense budget.

"We've got to address the threats that we know are the major threats and we're not doing it," Sen. Carl Levin, D-Mich., argued before his measure was rejected.

The Bush administration plans to deploy nine ground-based interceptor missiles (search) this year at Fort Greely, Alaska and have 20 deployed by 2005 or 2006. Levin's proposed cuts wouldn't affect those, but an additional 10 planned after that.

"This is numbers 21-30," he said, adding that the money proposed for those 10 could be used for the "many unfunded needs that we have" in homeland security and counterterror efforts.

Levin, ranking Democrat on the Senate Armed Services Committee, said officials have determined the No. 1 threat is "loose nukes" -- bomb material around the world that they fear could fall into the hands of terrorists. And he quoted a CIA (search) assessment that U.S. territory is more likely to be attacked with weapons of mass destruction that are not delivered by missile because they are less expensive and easier to develop and deploy in secret.

Arguing against Levin's measure, Sen. John Warner, R-Va., chairman of the Armed Services Committee, cited another CIA assessment saying the possibility of a missile attack on the United States is higher today than it was during most of the Cold War.

Sen. Jeff Session, R-Ala, said Levin's measure was yet another Democratic attempt to draw money from the program they oppose, and that it would harm its progress.

"Yes, there are a lot of needs in this country ... education, health care, homeland security ... that we believe we need desperately here in America," Sessions said.

"But we made a choice to field a missile defense system," he said of previous congressional approval.

Missile defense is an essential part of Bush's national security policy. It hasn't been as politically divisive as President Reagan's more elaborate "Star Wars" (search) program, but Democrats complain the administration is spending billions of dollars to deploy interceptors without conducting adequate tests to see if they will even work.

A report in April by the investigative arm of Congress called for more realistic testing.