The announcement appears to preclude any kind of top-level meeting or breakthrough ahead of the 50-day deadline for an agreement given by President Donald Trump.

Ukrainian and Russian officials ended their third round of peace negotiations in under an hour Wednesday — falling short of establishing a cease-fire but agreeing to a prison swap. The talks took place in Istanbul just over a week after President Trump threatened Russian President Vladimir Putin with “very severe tariffs” if he doesn’t commit to a cease-fire in Ukraine within 50 days.

The warring sides remain far apart after the third round of U.S.-brokered peace negotiations on Wednesday. But there was progress on humanitarian issues.