In one recent case, a leading expert on conflict resolution who's 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 no longer was 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's critical of President Bush's handling of Iraqi 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, Indonesia, 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 last 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 been excluded routinely from the president's domestic events and campaign rallies. This week, Knight Ridder and other 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 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 International Information Programs bureau, 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 couldn't be reached for comment. Seven calls made to two of his press officers and to State Department spokesman Sean McCormack weren't returned by the end of the day Friday.

The effort, known as the "U.S. Speakers/Specialist Program," is part of a public diplomacy effort to change negative foreign opinions of the United States. It's overseen by Undersecretary of State Karen Hughes, although the questionable 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 hadn't reached the level of the mid-1980s, when Reagan administration appointees at the now-defunct U.S. Information Agency compiled a blacklist of 95 people banned from the agency's overseas speaking program. On it were veteran TV anchor Walter Cronkite, 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.

State Department e-mails obtained by Knight Ridder show that in October, the U.S. Embassy in Tel Aviv, Israel, and the U.S. Consulate in Jerusalem asked for Phillips to participate in a Nov. 9 video teleconference discussion with American officials and Israeli and Palestinian conflict-resolution practitioners. The embassy's request cited Phillips' long experience in conflict resolution.

On Oct. 26, an official in Washington wrote back: "We are currently researching alternate conflict resolution experts who would be better suited to address this topic and with whom IIP has a great deal of successful experience."

After a conversation with State Department headquarters that same day - the contents of which weren't disclosed - a U.S. diplomat in Jerusalem wrote Washington that she would "talk over the options" and "get right back to you with our ... preferred next step, okay?"

Officials in Washington proposed four other conflict-resolution experts, but the teleconference, already delayed, was canceled in the second half of November.

In the case of Obama, after the request from Jakarta came in Jan. 12, political appointees in the International Information Programs bureau argued in e-mails that a Republican senator should be sent as well.

That's standard State Department practice when individuals go out to discuss American party politics. But the Jakarta U.S. Embassy had asked for him to speak about diversity, not politics.

Approval for department officials to contact Obama was delayed until June 13.

The senator's office said it was unaware of the controversy.

State Department records show that administration critics occasionally have gone overseas on government-sponsored engagements.

Anthony Cordesman of the Center for Strategic and International Studies has gone to Iraq, Australia, Tanzania and elsewhere. He frequently has critiqued the U.S. anti-insurgency effort in Iraq.

Larry Diamond, a Stanford University authority on democratization, went to Ghana and Nigeria last February, although that was before his own critical account of the Iraq effort was published last summer.

But Temple University professor Mahmoud Ayoub, an expert on interreligious dialogue who went on a half-dozen State Department-sponsored trips after the Sept. 11, 2001, terrorist attacks, was turned down without explanation last summer for a grant to teach a course in Indonesia.

Ayoub said he wasn't accusing the department of a political vendetta and that he still participated in a program to host international visitors in this country.

"I would hope there is no political reason," he said. "It's a very sad thing when we don't have the freedom to express ourselves."

Coleman Barks, the translator of a 13th-century Persian poet from Islam's mystic Sufi tradition, was the first U.S.-sponsored speaker to go to Afghanistan in 25 years. But two officials said he angered Feldman by criticizing the Iraq war in a subsequent conversation with him.

Barks, who lives in Athens, Ga., said he didn't know if he'd been excluded from further tours.