MOSCOW, April 26 (Reuters) - Russia is reserving judgment on whether to recognise Ukraine's presidential election on May 25, Russia's ambassador to the United Nations, Vitaly Churkin, told the Komsomolskaya Pravda newspaper in an interview published on Saturday.

"We are watching how they take place," he said. "If tanks will be shooting, then of course (recognition) is absurd. But for now we aren't making categorical declarations and conclusions in advance."

Churkin also said it was possible the elections may not happen.

Western leaders have agreed to impose new sanctions against Russia as they regard a stable and peaceful election as an urgent step. Ukraine has accused Russia of trying to undermine the vote.

Churkin also told Komsomolskaya Pravda that the Kiev government "must take the first step" to implement an international agreement to defuse the Ukraine crisis reached in Geneva on April 17 "because they consider themselves the government".

"They need to do more than those protesting in eastern Ukraine: disarm (the nationalist group) Right Sector, free occupied administrative buildings. But the most important thing is to begin dialogue with the east. So far they haven't lifted a finger," he said.

Western governments have accused Russia of doing nothing to implement the Geneva agreement, which said illegal armed groups must be disarmed and illegally occupied buildings and public places vacated.

(Reporting By Jason Bush; Editing by Erica Billingham)