KIEV, Ukraine (AP) — U.S. Vice President Joe Biden criticized Russia on Friday for its role in eastern Ukraine, urging Moscow to uphold a cease-fire in the war-torn region as he visited Kiev on the anniversary of the start of the country's anti-government protests.

Biden said Western sanctions against Russia would not be lifted until Moscow does more to enforce the cease-fire. Over 900 people have been killed and fighting has continued in eastern Ukraine since a truce began in September, and the conflict has claimed at least 4,300 lives since April, according to the U.N.

"If Russia were to fulfill these commitments and respect Ukrainian sovereignty and territorial integrity, we could begin a rational discussion about sanctions," Biden said. "But that's not what has happened. Instead we've seen more provocative actions, more blatant disregard for the agreement."

In a meeting with Prime Minister Arseniy Yatsenyuk, Biden said the United States and its allies in Europe and the G-7 would work "to increase the costs to Russia if it continues on its current course of blatantly violating Ukraine's sovereignty and territorial integrity."

Biden stopped short of announcing that the United States would provide lethal military aid to Ukraine. The United States has already given Ukraine $53 million in non-lethal aid.

The protests that began a year ago in Kiev led to the ouster of Ukraine's former pro-Russian president in February. Russia then annexed the Black Sea peninsula of Crimea in March and began backing a pro-Russian insurgency in eastern Ukraine.

Ukrainian President Petro Poroshenko and Yatsenyuk were shouted at Friday when they laid a wreath at a memorial to victims of sniper attacks in February. The protesters demanded a full government investigation into the deaths.

Biden later made an unscheduled visit to a separate memorial to the victims, a fence that has photos of dozens of those killed.

___

(An earlier version of this story incorrectly said the memorial visited by Poroshenko was at the city's central square.)