Francois Hollande, Angela Merkel and David Cameron held phone separate talks to discuss the situation in eastern Ukraine days after a Malaysia Airlines jet crashed, killing 298 people on board after what is believed to have been a strike by a surface-to-air missile.
Concerns have been mounting that the separatists are blocking access to key evidence and to the bodies of the passengers, scores of which were moved from the crash site to a train today.
A French presidency statement after the calls similarly warned that "consequences" would be drawn at Tuesday's meeting "if Russia does not immediately take the necessary measures".
It said the three leaders had agreed to call on Putin to pressure the rebels into allowing rescuers and investigators "free and total access to the site of the MH17 flight disaster to accomplish their mission".
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Cameron had already raised the prospect of fresh EU sanctions against Russia, warning in the Sunday Times that Moscow should be held accountable if it was confirmed that MH17 was downed by a missile fired from an area held by pro-Russian separatists in Ukraine.
The European Union has so far hit 72 Ukraine and Russian figures with travel bans and asset freezes over the crisis, but divisions over how far to go given some member states' close economic ties with Russia has left Brussels trailing Washington.
But so far, EU leaders have only agreed to widen the scope of current Phase 2 sanctions, including punishing Russian firms, and the new list of targets is expected to be ready by the end of the month.