Congress is poised to defy President Bush by proposing to ban the use of private contractors to interrogate detainees and to restrict the use of private security guards in combat zones.

The provisions to scale back the outsourcing of military work are buried deep in the $612.5 billion defense authorization bill (S 3001) that the Senate plans to take up this month. The House-passed version (HR 5658) contains an identical ban on private interrogators and similar limitations on the use of private security guards.

White House officials have threatened a veto of the House bill over its prohibition on private interrogators and are likely to take the same view of the Senate’s version.

The White House statement on the House bill said the ban on private interrogators “would unduly limit the United States’ ability to obtain intelligence needed to protect Americans from attack.”

Moreover, administration officials “strongly oppose” the restrictions on hiring private security guards, said Corinne E. Hirsch, a spokeswoman for the Office of Management and Budget. The White House has not yet said whether Bush would veto the bill over such a provision.

The House-passed defense authorization bill contains a number of other provisions that could trigger a veto. But they are unlikely to end up in a Senate or final version of the bill.

Barring some reversal on the Senate floor, the contractor provisions will be in both versions of the bill, directly defying the presidential veto threat.

The Defense bill authorizes the Pentagon and the Energy Department to spend money on national security programs each year. It also sets Defense policies and authorizes hiring and payment of military personnel.

The provision to ban private interrogators came after news that contractors had ordered or committed abuses at prisons such as Abu Ghraib in Iraq. Both the House and Senate versions of the ban would take effect one year after enactment, with exceptions for certain related jobs, such as interpreters and information technology specialists.

The House added the provision on the floor in an amendment by David E. Price, D-N.C., who argued that interrogations are inherently government functions.

“We should all be able to agree that interrogation should be carried out by individuals who are well trained, who fall within a clear chain of command and who have a sworn loyalty to the United States, not by corporate, for-profit contractors,” Price said on the House floor late last month.

Republicans replied that the best interrogators sometimes work for contractors.

“So the bottom line is, this amendment ties our hands and prevents us from using the most effective, most qualified people to conduct interrogations,” said William M. “Mac” Thornberry, R-Texas. “And when you do that, you are limiting the information that is necessary to keep this country safe.”

The provision to restrict the use of private security guards came after reports that such personnel employed by Blackwater Worldwide and other firms had killed Iraqi civilians. The bills would require the Pentagon to write rules defining the conditions in which security operations are military missions that should not be outsourced.

Rep. Jan Schakowsky, D-Ill., author of the security guards provision, said in a statement that contractors that have operated outside the Defense Department chain of command “have often damaged the credibility of our military and harmed our relationship with the Iraqi government.”