The United States said on Friday that continued aggression by Russia would provoke a response by Nato and a greater alliance presence in Eastern Europe.

"What we are demonstrating is that if Russia continues this pattern of aggressive behavior, there will be a response and there will be a greater presence in Eastern Europe," White House Deputy National Security adviser Ben Rhodes said.

"We are going to do what is necessary to defend the alliance and the eastern members of the alliance," he told a news conference on the sidelines of the Nato summit in Warsaw.-Reuters