U.S. U.S. Ambassador to NATO Julianne Smeck said that the U.S., its allies and Russia are still signaling to Russia that they will respond to any escalation by inflicting “massive economic sanctions” and other consequences.

She said that she was open to considering all possibilities, speaking on Thursday to CNBC’s Hadley Gamble.

Smith replied to questions about the limits of effectiveness of sanctions. Vladimir PutinHe has made a decision about what to do next with troops he deployed at the Ukraine border.

“We’re trying sharpen the choice to President Putin as we weigh his options here,” she said.

Fears of war between Moscow-Kyiv have risen due to the increasing military presence on the border. The U.S., other Western countries and Russia have failed to make much progress in negotiations. Russia has also not been pressured by sanctions or the possibility of punishing it.

The former president of Ukraine, Petro Poroshenko, previously told CNBC that sanctions on Nord Stream 2 would make Russia weaker and discourage Putin from attacking. Nord Stream 2 refers to a pipeline project which would allow gas to be transported from Russia into Europe and bypass Ukraine.

The Kremlin has denied it is planning to invade Ukraine, in what would be a repeat of its illegal annexation and occupation of Crimea in 2014.

Smith stated separately that Smith believes the decision to send 3,000 U.S. troops closer to UkraineThis was done partly to provide reassurance to allies and deterrent.

When asked if this could be considered provocative for Russia, she said that there are many numbers that differ, with estimates that 127,000 soldiers have been stationed near Ukraine’s borders.

“I think we’re really comparing apples with oranges,” she stated, noting that U.S. troops will not move to Central and Eastern Europe permanently and aren’t going into Ukraine.