U.S. Vice President Joe Biden on Friday condemned Russia's behaviour in Ukraine as "unacceptable" and said Moscow should abide by a September peace deal and pull its military forces out of the country.
Addressing himself rhetorically to Russian leader Vladimir Putin after holding talks with Ukrainian President Petro Poroshenko, Biden said: "Do what you agreed to do, Mr. Putin."
The high-level U.S. visit to Kiev took place with diplomatic efforts stalled on ways of restarting the peace deal signed by Ukraine, Russia and pro-Moscow separatists fighting in the east.
Russia says it supports the rebel cause but denies Ukrainian and Western accusations that it has sent in its own regular troops and armour to bolster the separatists. Moscow says any Russians taking part are volunteer fighters.
Both sides have also accused each other of violating the ceasefire and Ukraine said on Friday that its territory had come under cross-border artillery fire from inside Russia for the first time since the truce came into force.
Biden's visit to Kiev took place on the first anniversary of a decision by the government of Ukraine's then-president Viktor Yanukovich to ditch a political and trade pact with the European Union in favour of closer ties with Russia.
The move provoked protests from tens of thousands of Ukrainians and led to the ousting of the Moscow-backed Yanukovich in February. It triggered the worst confrontation between Russia and the West since the Cold War after Russia annexed Crimea in March and backed the eastern separatists.
PROTESTS
Thousands gathered on Kiev's Independence Square on Friday in remembrance of the start of the protests, holding a candle-lit minute's silence, many decked out in the blue and yellow colours of the Ukrainian flag.
Poroshenko, a former confectionary magnate who was elected president in May, said his country's future remained at risk.
"More than ever we need national unity or else the conflict within the country will destroy us," he said in a statement to the nation posted on his website.
Tensions still simmering in Ukraine's war-racked society came to the surface when Poroshenko went to pay tribute to the 100 or so protesters who were killed in February by police snipers before Yanukovich fled into exile in Russia.
Relatives of those killed, frustrated by the government's failure to bring officials of the Yanukovich government to book, shouted, "Where are their killers?" and "Down with Poroshenko!" and also condemned him for failing to keep a promise to confer the title of national hero on the victims.
Poroshenko later returned to the scene to pledge that he would sign a decree to officially designate the victims as national heroes as promised.
Biden, appearing alongside Poroshenko, condemned Russia's annexation of Crimea and backing for the separatists and said Washington would always support a democratic, reformist Ukraine.
However he made no mention of fresh military aid which Kiev has appealed for. Biden's office said about $118 million in U.S. aid had been committed to Ukraine's security forces but did not specify how much was new.
Non-lethal aid, the statement said, includes "body armor, helmets, vehicles, night and thermal vision devices, heavy engineering equipment, advanced radios, patrol boats, rations, tents, (and) counter-mortar radars."
The first three of 20 counter-mortar radar systems were flown to Ukraine aboard a cargo aircraft accompanying Biden's flight, the Pentagon said on Friday.
Pending Congressional approval, the White House will commit $20 million to supporting reform of Ukraine's law enforcement and justice sectors, Biden's office added.
