The acquisition will significantly expand CACI's opportunities for business growth in its Enterprise IT, Intelligence Services, and other key market areas.

With a purchase price of $550 million, the transaction is expected to add approximately $1 billion of annual revenue to CACI.

Headquartered in Reston, Virginia, NSS provides highly specialized and differentiated strategic solutions, services, and products for the country's most sensitive national security agencies and DoD critical missions. NSS employs approximately 4,000 professionals worldwide, of whom over 90 percent possess security clearances.

Dr. J.P. (Jack) London, CACI Executive Chairman and Chairman of the Board, said, "We welcome the highly skilled and experienced employees from National Security Solutions to CACI's team of talented and dedicated professionals. The combined expertise of our organizations is underscored by our shared cultural commitment to good character and ethics. Together, we will further drive excellence and innovation for our customers and long-term value for our shareholders."

ABOUT CACI

CACI provides information solutions and services in support of national security missions and government transformation for Intelligence, Defense, and Federal Civilian customers. A Fortune magazine World's Most Admired Company in the IT Services industry, CACI is a member of the Fortune 1000 Largest Companies, the Russell 2000 Index, and the S&P SmallCap600 Index. CACI provides dynamic careers for over 20,000 employees worldwide.

The U.S. sources said Washington had no reason to believe Tehran was involved in the kidnapping and did not believe the trio were being held in Iran, which borders Iraq.

"They were abducted because they are Americans, not for personal or financial reasons," one of the Iraqi sources in Baghdad said.

The three men are employed by a small company that is doing work for General Dynamics Corp (GD.N), under a larger contract with the U.S. Army, according to a source familiar with the matter.

The Iraqi government has struggled to rein in the Shi'ite militias, many of which fought the U.S. military following the 2003 invasion and have previously been accused of killing and abducting American nationals.

Baghdad-based analyst Hisham al-Hashemi, who advises the government, said the kidnappings were meant to embarrass and weaken Iraqi Prime Minister Haider al-Abadi, who is trying to balance his country's relations with rival powers Iran and the United States.

"The militias are resentful of the success of the army in Ramadi which was achieved with the support of the U.S.-led coalition and without their involvement," he said.

Shi'ite militias were kept out of the battle against Islamic State in Ramadi for fear of aggravating sectarian tensions among the Sunni population in the western city.

Baghdad touted the military's advance there last month, with backing from coalition airstrikes, as evidence of a resurgent army after it collapsed in 2014.

The State Department said it was working with Iraqi authorities to locate Americans reported missing, without confirming they had been kidnapped.

Asked about the kidnapping at the daily U.S. State Department news briefing on Tuesday, spokesman John Kirby said: "The picture is becoming a little bit more clear in terms of what might have happened." He provided no details...