WASHINGTON  Last fall, Blackwater Worldwide was in deep peril.

Guards for the security company were involved in a shooting in September that left at least 17 Iraqis dead at a Baghdad intersection. Outrage over the killings prompted the Iraqi government to demand Blackwater’s ouster from the country, and led to a criminal investigation by the F.B.I., a series of internal investigations by the State Department and the Pentagon, and high-profile Congressional hearings.

But after an intense public and private lobbying campaign, Blackwater appears to be back to business as usual.

The State Department has just renewed its contract to provide security for American diplomats in Iraq for at least another year. Threats by the Iraqi government to strip Western contractors of their immunity from Iraqi law have gone nowhere. No charges have been brought in the United States against any Blackwater guard in the September shooting, either, and the F.B.I. agents in Baghdad charged with investigating whether Blackwater guards have committed any crimes under United States law are sometimes protected as they travel through Baghdad by Blackwater guards.

The chief reason for the company’s survival? State Department officials said Friday that they did not believe they had any alternative to Blackwater, which supplies about 800 guards to the department to provide security for diplomats in Baghdad. Officials say only three companies in the world meet their requirements for protective services in Iraq, and the other two do not have the capability to take on Blackwater’s role in Baghdad. After the shooting in September, the State Department did not even open talks with the other two companies, DynCorp International and Triple Canopy, to see if they could take over from Blackwater, which is based in North Carolina.