The State Department has been using political litmus tests to screen private U.S. citizens before they can be sent overseas to represent the United States, weeding out critics of the Bush administration's Iraq policy, according to department officials and internal e-mails.

In one recent case, a leading expert on conflict resolution who is a former senior State Department adviser was scheduled to participate in a U.S. Embassy-sponsored videoconference in Jerusalem last month, but at the last minute he was told that his participation was no longer required.

State Department officials explained the cancellation as a scheduling matter. But internal department e-mails show that officials in Washington pressed to have other scholars replace the expert, David L. Phillips, who wrote a book, "Losing Iraq," that is critical of President Bush's handling of Iraq reconstruction.

"I was told by a senior U.S. official that the State Department was conducting a screening process on intellectuals, and those who were against the Bush administration's Iraq policy were not welcomed to participate in U.S.-government-sponsored programs," Phillips said.

"The ability of the United States to promote democracy effectively abroad is curtailed when we curtail free speech at home, which is essential to a free society," he said.

In another instance of apparent politicization, a request by the U.S. Embassy in Jakarta to arrange a visit by Sen. Barack Obama (D-Ill.), who lived in Indonesia when he was young, was delayed for seven months. The visit never occurred.

A prominent translator of Islamic poetry who toured Afghanistan to rave reviews in March fell out of favor when he later criticized the Iraq war in front of a department official, two U.S. officials said.

The practices appear to be the latest examples of the Bush administration's efforts to tightly control information, maintain "message discipline," and promote news about the United States and its policies.

Bush opponents have routinely been excluded from the president's domestic events and campaign rallies. This week, news organizations reported that the Pentagon has paid Iraqi journalists and newspapers to publish positive stories about the U.S. reconstruction effort there.

Current and former officials involved with the State Department's overseas speakers program said potential candidates were vetted -- via Internet searches, for example -- for any comments or writings that criticized White House policy.

"There's definitely a political litmus test. You don't have to be a Republican, but you better not have said anything against them," one official said.

The official said he knew of no blacklist of banned scholars. "But there certainly is a 'white list' of those who can go," he added.

He and others agreed to discuss the State Department practices only on the condition of anonymity, saying they feared retaliation for exposing them.

Late this week, after Knight Ridder inquired about the litmus tests, Alexander Feldman, the head of the department's Bureau of International Information Programs, which runs the speakers program, sent a memo to his employees warning that "no one is to speak to the press without following the procedures" and getting approval. Knight Ridder obtained a copy of the memo.

Feldman, a political appointee and former media executive, was traveling and could not be reached for comment. Seven calls made to two of his press officers and to State Department spokesman Sean McCormack were not returned by the end of the day Friday.

The U.S. Speaker and Specialist Program is part of a public diplomacy effort to change negative foreign opinions of the United States. It is overseen by Undersecretary of State Karen Hughes, although the screening practices reportedly began before she took up her post in September.

Using political views to screen candidates appears to violate the speaker program's charter, which is to present a "range of responsible opinion" in the United States to overseas audiences, not to hawk a particular administration's policies.

The officials who were critical of current practices said the situation had not reached the level of the mid-1980s, when Reagan administration appointees at the now-defunct U.S. Information Agency compiled a blacklist of more than 80 people banned from the agency's overseas speaking program. On it were veteran TV anchor Walter Cronkite, civil rights activist Coretta Scott King and economist John Kenneth Galbraith.

"Every administration has made an effort to check the political correctness of speakers who go out," one State Department veteran said.