President Obama congratulated Ukraine's president-elect Petro Poroshenko on his victory and offered the support of the US as he attempts to "unify his country".
A White House statement said Obama congratulated Poroshenko and offered "the full support of the United States as he seeks to unify and move his country forward."
The leaders will talk again next week, the White House said.
More top news
The Football Association has announced it has received an offer to buy Wembley Stadium.
Abbas Edalat, a professor in computer science and maths at Imperial College London, has reportedly been held in custody since April 15.
The Russian ambassador in The Hague told ITV News that “Russia never lies” as he set out plan to prove the attack in Douma was staged.