U.S. Vice President Joe Biden spoke by phone on Friday, August 19 with Ukrainian President Petro Poroshenko and both leaders expressed concern over a recent surge in fighting in eastern Ukraine, where Kiev is fighting pro-Russian separatists, the White House said, according to Reuters.

"The Vice President relayed that the United States had sent a message to Russia that the world is watching and underscored the need to de-escalate the situation. He also urged Ukraine to show restraint," the White House statement said.