WASHINGTON (AP) — U.S. officials said Friday that President Barack Obama may scrap plans to attend an international summit in Russia this summer and could also halt discussions on deepening trade ties with Moscow, raising specific possible consequences if Russia should intervene in Ukraine. Obama himself bluntly warned of unspecified “costs” for Russia.

“Any violation of Ukraine’s sovereignty and territorial integrity would be deeply destabilizing,” Obama declared. Such action by Russia would represent a “profound interference” in matters that must be decided by the Ukrainian people, he said.