The International Criminal Court (ICC) has given prosecutors a one-week deadline to bring evidence against Kenya’s president or to drop charges.
Further delays in President Uhuru Kenyatta’s case would be “contrary to the interests of justice”, it ruled.
Mr Kenyatta was the first head of state to appear before the court since he was formally charged in 2012 with crimes against humanity, which he denies.
The prosecution has repeatedly asked for more time to build its case.
It says witnesses have been bribed and intimidated, and the Kenyan government has refused to hand over documents vital to the case.
Mr Kenyatta denies inciting violence following the disputed 2007 elections in order to secure victory for then-President Mwai Kibaki and says the ICC case is political.
Rejecting the prosecution’s latest request for a delay, the court’s judges said it needed to indicate within a week whether it would withdraw charges or that the “evidentiary basis has improved to a degree which would justify proceeding to trial”.
Mr Kenyatta won presidential elections in 2013, with the backing of Mr Kibaki.
He used the case against him to rally nationalist support by accusing The Hague-based court of meddling in Kenya’s affairs.
He is accused by the ICC prosecution of being “an indirect co-perpetrator” in the post-poll ethnic massacres of 2007/2008.
Some 1,200 people were killed in the violence and 600,000 were displaced.
Mr Kenyatta’s deputy William Ruto is on trial at the court on similar charges after his legal team’s efforts to throw out the case failed.
He and Mr Kenyatta were in opposite camps during the 2007 election, with Mr Ruto accused of fuelling violence to bolster opposition leader Raila Odinga’s chances of becoming president. He denies the charges.
Mr Ruto formed an alliance with Mr Kenyatta in the 2013 election, opening the way for him to become deputy president.
The court’s decision to charge Mr Kenyatta caused international controversy, with the African Union (AU) accusing it of “hunting” Africans because of their race.
The prosecution denied the allegation, saying it pursued justice impartially.