The recent Iraqi civilian deaths in a shootout involving guards employed by Blackwater USA has spurred renewed interest among Senate Democrats in pushing tougher rules for overseas security contractors.

But Republicans said Thursday that they would oppose those efforts because of Bush administration concerns.

Democrats have offered varied amendments to the fiscal 2008 defense authorization bill (HR 1585) that would address the role of security contractors.

The most comprehensive amendment is based on a bill (S 674) by Barack Obama, D-Ill. Democratic aides said Thursday they were working to get Obama’s measure included in the bill.

A Republican committee aide said the GOP opposed the amendment, in part, because “both the Justice Department and the Defense Department have raised ­serious substantive concerns.” They also cited procedural concerns, arguing that the Judiciary Committee would have jurisdiction over the measure and should review it.

Obama’s amendment would largely bring the Senate bill into line with the House version of the defense authorization bill (HR 1585), passed Aug. 5, which includes several provisions that would define the role of civilian security contractors in Iraq, mandate basic screening and establish rules of engagement for their ­operations.

In a Sept. 19 letter to Defense Secretary Robert M. Gates, Obama complained of a lack of transparency regarding security contractors and demanded to know what the Pentagon is doing to investigate the Baghdad shootings.

“As last weekend’s incident illustrates, little is known about what functions these security contractors are performing, how much their services are costing, what military and safety equipment they are provided and what rules of engagement they are following,” he wrote.

Obama’s language would extend the jurisdiction of U.S. law to cover contractors in Iraq and would place the FBI in charge of investigating their crimes.

The amendment also would require the Defense Department to reveal the size and makeup of its security contractor force and define the boundaries of its activities.

Democrats Jim Webb of Virginia and Claire McCaskill of Missouri have an amendment that would require contractors to report incidents resulting in death, injury, or property damage and would require that they be briefed on their obligations to comply with applicable U.S., Iraqi and international laws.

Webb also offered an amendment (S 1825) that would establish a wartime commission on contracting.

The commission would be required to investigate the extent of the federal government’s reliance on contractors and define what activities should be kept to government-employed personnel.

Lindsey Graham, R-S.C., and John Kerry, D-Mass., introduced an amendment Thursday that would direct the Defense Department to clarify implementation of a provision in the fiscal 2007 defense authorization law (PL 109-364) that places security contractors under the jurisdiction of the Uniform Code of Military Justice.

Without clarification, experts say it is unclear whether the law covers contractors employed by non-Defense Department agencies, such as the State Department, which hired the Blackwater guards implicated in last week’s shootings.

Many members said that until Congress acts to rein in the contractor workforce, they were content to let the Iraqi government prosecute crimes by civilian security contractors, such as the Blackwater shooters. “I think they are probably open to prosecution in Iraq,” said Senate Armed Services Committee member Ben Nelson, D-Neb., who was protected by Blackwater guards on his recent trip to Iraq.

As one of his last official acts on June 27, 2004, L. Paul Bremer III, who headed the Coalition Provisional Authority that ran Iraq after the U.S. invasion in 2003, extended contractors’ immunity from prosecution in Iraq for any incident involving their work.

However, legal experts disagree over whether that immunity is still in effect. ­Peter W. Singer, a senior fellow at the Brookings Institution, said the provisions granting immunity in 2004 don’t necessarily apply to the now-sovereign Iraqi government.

Senate Majority Whip Richard J. Durbin, D-Ill., in a floor speech Sept. 18 complained that it was time to do something about security contractors in Iraq. He singled out Blackwater in particular.

“Blackwater has enjoyed a charmed existence with the Bush administration from the start,” Durbin said. “This is another example of a firm that has been given millions of taxpayers’ dollars to do a job in Iraq without accountability, without the kind of disclosure, basic disclosure, which American taxpayers deserve and demand.”

The State Department announced earlier this week that it would set up a joint commission with the Iraqi government to explore issues related to U.S. security contractors in Iraq.

President Bush was asked about the Blackwater shooting at a news conference Thursday. He said he expects to speak with Iraqi Prime Minister Nouri al-Maliki about the incident next week at the United Nations.

“I’m confident he’ll bring it up,” Bush said. “I also appreciate the fact that he’s willing to work with the U.S. government to set up a commission to find out what actually happened. The folks like Blackwater who provide security for the State Department are under rules of engagement — in other words, they have certain rules. And this commission will determine whether or not they violated those rules.”