By Wangui Kanina
The move came as pressure mounted on Kenya's feuding parties to resolve a crisis triggered by the December 27 polls that has killed more than 1,000 people and uprooted some 300,000 others.
"It's a very clear warning to them that their actions have put them in jeopardy of losing their visas," said State Department spokesman Tom Casey. "We are going to continue to evaluate these cases over the next few days here to see whether in fact they ought to have their visas revoked."
The violence has shattered Kenya's image of stability, horrifying locals, neighbouring states and world powers alike.
"I have not received any letter and even if I received it, I would write back 'Heaven is not in your country, it is right here in my country,'" Justice and Constitutional Affairs Minister Martha Karua, one of Kibaki's toughest backers, told reporters.
Those warned were "individuals from both sides, both major political movements, who have some standing in their parties and who we feel have been unhelpful", said a U.S. official, who wished not to be named.
TALKS PROCEED
A string of outside diplomats also came through, including European Union aid chief Louis Michel, who met with Annan, Kibaki and opposition leader Raila Odinga.
Having agreed on principles to stem violence and help refugees, negotiators at the Annan talks are now stuck on the original bone of contention -- who won the December vote.
"The topic is a crucial one and proves divisive at times, but the talks proceeded in a good spirit, moving more slowly than in previous sessions," a U.N. spokesman said.
Foreign ministers of the regional bloc IGAD were also in town to meet Annan and among themselves, while leaders of another regional group, the East African Community, indefinitely postponed a visit due to start on Friday.
Kibaki was recognised last week as a head of state at an African Union summit, a meeting Kenya's opposition tried but failed to get into.
On Thursday police also said they would charge one of their officers with murder after he was filmed shooting two protesters in Kisumu last month in what rights groups and the opposition denounced as extrajudicial killings.
(Additional reporting by Duncan Miriri, Daniel Wallis, Bryson Hull, Joseph Sudah; Writing by Daniel Wallis, Editing by Bryson Hull and Michael Winfrey)
