WASHINGTON (REUTERS) - US Secretary of State John Kerry on Saturday warned Russia that the United States and its G7 partners would 'raise the costs' Moscow could face unless it curbed weapons flowing into Ukraine and cut ties with pro-Russia separatists.

Kerry "underscored the commitment of the United States and G7 partners to raise the costs for Russia if it does not end the flow of weapons across the border and break with separatists," a senior State Department official said of Kerry's call on Saturday with Ukrainian Prime Minister Arseny Yatseniuk.

Kerry also expressed condolences for the deaths of 49 servicemen who were killed when pro-Russian separatists shot down an army transport plane in east Ukraine on Saturday.