Correction: An earlier version of this article incorrectly said that a Senate Homeland Security and Governmental Affairs Committee hearing on visa security was scheduled for Thursday. The hearing was held Wednesday. This version has been corrected.

Heightened security concerns in the United States have stalled the immigration process for tens of thousands of Iraqis who worked for the U.S. government or American firms in Iraq and hope to move to the United States, according to U.S. officials and refugee advocates.

A special program meant to distribute 25,000 visas to Iraqis who worked for the U.S. government has admitted just 7,000 since it started in 2008, officials said this week. In addition, the U.S. Refugee Admissions Program, a global program that also admits Iraqis, will admit about 6,000 Iraqis this year, down from 18,000 in fiscal 2010.

In a demonstration of the slowdown facing about 30,000 Iraqis, refugee advocates said just 50 were granted entry to the United States through the programs in April, compared with thousands in previous months. Officials at the U.S. Embassy in Baghdad contacted this week did not dispute the figures and did not provide more recent numbers.

American officials said there are no plans to end either program, but refugee advocates complain that the U.S. government is reneging on promises made to those who risked their lives during the war. Advocates have also said that reprisal attacks on Iraqis who worked for the U.S. military or contractors will probably increase as U.S. troops draw down across the country.

The programs “are, by almost every metric, a failure,” said Kirk Johnson, founder of the List Project, which tracks the status of Iraqis who worked for U.S.-based entities. “There are a lot of open, unused slots every year that are just sitting there because of complications.”

Although several State Department officials acknowledged that sustained interest in the programs and a small number of personnel and secure facilities to conduct interviews are contributing to the backlog, they blamed most of the delay on visa vetting procedures enacted in recent months by the Department of Homeland Security.

Screeners now conduct more thorough background and biometric checks of applicants, in addition to checks against several databases, according to DHS officials familiar with the program. Also, officials said, new “pre-departure” checks conducted shortly before a refugee is scheduled to leave for the United States, are catching potentially disqualifying information that might arise after an initial screening.

The results of some “pre-departure” checks have forced officials to physically remove Iraqis from flights shortly before they head to the United States, according to refugee advocates and embassy officials.

“There are a number of issues that need to be resolved before a person can be admitted,” Eric P. Schwartz, assistant secretary of state for the Bureau of Population, Refugees and Migration, said in an interview. “Because of the additional issues that arise, it by definition causes additional time requirements.”

Schwartz urged critics to remain patient. “Advocates for refugee protection also have to be advocates for responsible security procedures,” he said.

In May, lawmakers and security experts raised fresh questions about visa security procedures after two Iraqis living in Kentucky were arrested on terrorism charges. The men, admitted to the United States under the USRAP program, were charged with sending cash, explosives and missiles to Iraq for use against Americans.

Administration officials in Baghdad and Washington, congressional aides and refugee advocates disputed suggestions of a direct link between the May arrests and the slowdown, but some suggested that the enhanced screening contributed to the arrests.

The Senate Homeland Security and Governmental Affairs Committee is scheduled to hold a hearing Wednesday to review visa security issues. Although the hearing was planned before the arrests, aides said lawmakers would probably point to them as examples of potential security vulnerabilities.

About 80 percent of Iraqis admitted by the visa program served as translators for the U.S. military, officials said. Ten percent of Iraqis admitted by USRAP, the broader refugee program, worked for American businesses, according to government statistics.

At least 22,000 people in Iraq are waiting to be admitted to USRAP, embassy officials said. About 3,800 Iraqis living in Jordan are awaiting final security interviews, and 8,500 Iraqis living in Syria have indicated interest. But the Syrian government is withholding visas for Homeland Security officials needed to conduct interviews there, U.S. officials said.

Among the tens of thousands waiting in Iraq are Haider Abduwahab and Ghassan Enad. The men once served as bodyguards for NBC News crews but now protect a nearly empty Baghdad hotel where hundreds of journalists roamed the hallways at the start of the U.S. invasion. The lack of business gives them too much time to sit and wonder whether they’ll ever have a chance to leave Iraq and start over in the United States.

“We feel like we’re stuck. We don’t know if we’ll make it or not,” Abduwahab said.

Abduwahab, 35, applied for the refu­gee program in September 2009 and completed all of the necessary interviews and medical tests within a year. He’s in a holding pattern as he waits to move to the United States with his wife, three children and parents.

“Sometimes if you try to move to a safer place, you hesitate because they might call and it’ll be time to go,” he said. “You might want to buy a new car or perhaps open a small store, but you can’t because you’re waiting.”

Enad, 31, applied for a visa in November 2009 and later received an e-mail with a case number. An interview was scheduled, then canceled, and he hasn’t heard back since.

Special correspondent Aziz Alwan contributed to this report.