Timothy Williams | NYTimes.com 

Blackwater Worldwide, the security firm whose guards killed 17 Iraqi civilians on a crowded Baghdad street in 2007, will not receive an operating license from the Iraqi government, a decision that will likely force American diplomats here to make new arrangements for their personal protection, officials said Thursday.

Unlike many security contractors in Iraq, Blackwater has been operating without an Iraqi government license, although it had recently applied for one.

The request was turned down during the past few weeks by the Iraqi government, officials said.

“They presented their request, and we rejected it,” said Ala’a Al-Taia, an official with Iraq’s Interior Ministry. “There are many marks against this company, specifically that they have a bad history and have been involved in the killing of so many civilians.”

The decision was first reported in The Washington Post.

An official at the United States Embassy in Baghdad said Thursday that the decision was being studied. Blackwater provides personal security to American State Department employees in Iraq, including the ambassador.

“We have been informed that Blackwater’s private security company operating license will not be granted,” the official said, speaking on condition of anonymity because she lacked permission to discuss the topic to a reporter. “We don’t have specifics about dates. We are working with the government of Iraq and our contractors to address the implications of this decision.”

Anne Tyrrell, a spokeswoman for Blackwater Worldwide, said Thursday that the company had not yet received official notification that its Iraqi license would not be granted.

“If that is the case,” she said, “we will respect the laws of Iraq and follow the direction of our U.S. government customers to insure that we are compliant with our contractual obligations as well as the rules of Iraq.”

It appears likely that Blackwater will remain in Iraq at least until spring, when a joint Iraqi-American committee is scheduled to complete guidelines for private contractors operating in Iraq, officials said. The State Department extended its contract with Blackwater in April 2008, despite its lack of an Iraqi license to operate.

The Iraqi government has sought in the past to expel Blackwater over concerns of inappropriate use of force, but American officials in Iraq who rely on the company’s heavily armed guards for security have said they had no alternative but to continue using the North Carolina-based security contractor.

Security contractors working in Iraq lost immunity from prosecution under Iraqi law on Dec. 31 as part of the status-of-forces agreement signed by the United States and Iraq. The agreement also strengthens the Iraqi government’s hand with United States officials to enforce its decision to not allow Blackwater to operate.

The immunity issue had been a priority for the Iraqi government since the Sept. 16, 2007, shooting in Baghdad’s Nisour Square. Blackwater’s guards, riding in a convoy through the square, opened fire on Iraqi civilians. The guards apparently believed they were being fired on.

Last month, five Blackwater guards were charged in the United States with manslaughter in connection to the shooting. They pleaded not guilty. A sixth guard, who pleaded guilty to manslaughter, is cooperating with prosecutors.

Iraq’s decision to ban the firm did not come without warning. In 2008, the State Department’s inspector general issued a report that said that there was a “real possibility” that Blackwater might not be licensed by the Iraqi government to continue to protect American diplomats in Baghdad in 2009.