By Rachel Huggins - 07/22/14 08:08 PM EDT
President Obama spoke with Dutch Prime Minister Mark Rutte Tuesday afternoon, hours after a morning visit to the Dutch Embassy in Washington to sign a condolences book for victims of the Malaysia Airlines crash.
In the phone call placed on Air Force One, Rutte thanked Obama for extending his support and the leaders talked about the latest developments in the Ukraine investigation.
Nearly 300 people were killed last week on the flight bound for Malaysia; the Netherlands was hardest hit, losing 193 citizens.
They also discussed concerns that Russia was continuing to send weapons and fighters across the border to support the separatists.
Both agreed the European Union and United States must remain united and that Russia will face increasing costs if it continues its support for violent separatists and fails to cease its efforts to destabilize Ukraine, the White House said in a statement about the call.
"The president welcomed the action taken today by the European Union's Foreign Affairs Council strongly condemning the actions leading to this tragedy and preparing additional sanctions against those destabilizing Ukraine," according to the White House.