Western diplomats have warned of “growing insecurity” in Kenya ahead of Thursday’s presidential election re-run, boycotted by the main opposition.
Inflammatory rhetoric and attacks on the election commission made it more difficult to hold a legitimate poll, the 20 envoys said.
Kenyan prosecutors said opposition leader Raila Odinga’s sister would be charged with inciting violence.
Mr Odinga has vowed to disrupt Thursday’s poll with a mass protest.
He says the vote cannot be held before key reforms, including the sacking of Independent Electoral and Boundaries Commission (IEBC) officials, are implemented.
About 70 people have been killed in violence since the IEBC declared President Uhuru Kenyatta the winner of elections on 8 August.
The Supreme Court of Appeal annulled his victory, saying the poll was marred by irregularities and illegalities.
And Mr Odinga says nothing has changed since.
The foreign envoys said they were concerned about the “deteriorating political environment” in East Africa’s biggest economy.
“It is easier to tear down than to build up. But it is dangerous, and it must stop,” US ambassador Bob Godec said in a statement on behalf of the 20 diplomats, including those of France, Germany and the UK.
Last week, a senior member of the IEBC fled to the US amid death threats.
Roselyn Akombe said the commission was under political “siege”, unable to reach consensus or take any decisions.
After meeting IEBC chairman Wafula Chebukati on Monday, Mr Kenyatta said he expected Thursday’s poll to go ahead.
“We have made funds available for the IEBC to do its job. Now they really should deliver,” he added in a statement.
Kenya’s prosecuting authority said Mr Odinga’s sister, Ruth Odinga, would be charged with entering an election centre without permission, and causing malicious damage to property during a training session for election officials in the opposition stronghold of Kisumu in western Kenya.
Opposition lawmaker Fred Outa would be charged with Ms Odinga, it added.
She is a former deputy governor of Kisumu State.
Mr Godec called for an end to attacks on IEBC staff, adding that “no-one is obliged to stand for office, or to vote if they do not wish to”.
The IEBC has said that Mr Odinga’s name will remain on the ballot paper, along with that of six minor candidates who obtained about 1% of the vote between them in the August poll.
The electoral commission said Mr Kenyatta had won the August vote by a margin of 1.4 million votes – or 54% of the total, compared to Mr Odinga’s 45%.