U.S. Ambassador to the United Nations Samantha Power said Sunday that reported attacks by pro-Russia militia on areas in eastern Ukraine appear to be connected to the Russian government and that the United States is prepared to intensify sanctions against Russia if its actions continue.

"Well, it has all the telltale signs of what we saw in Crimea," Power said on ABC's "This Week with George Stephanopoulos." "It's professional, it's coordinated, there's nothing grass-roots-seeming about it. The forces are doing in each of the six or seven cities that they've been active in exactly the same thing. So certainly it bears the telltale signs of Moscow's involvement."

Ukrainian authorities launched an “anti-terrorist” campaign Sunday against pro-Russian gunmen and Ukrainian officials are suspicious that Russia is involved.

"I think we've seen that the sanctions can bite. And if actions like the kind that we've seen over the last few days continue, you're going to see a ramping up of those sanctions," Power said.

Sen. John McCain (R-Ariz.) said the United States should shore up Ukraine's armaments in the ongoing crisis.

"We ought to at least, for God's sake, give them some light weapons with which to defend themselves," McCain said on CBS's "Face The Nation." He added that some in the Ukrainian government "feel abandoned" by the United States.

Vice President Biden plans to travel to Kiev later this month, the White House announced Saturday.

Questioned on reports about a recent poison gas attack in Syria, Power said the U.S. is trying to confirm what happened.

"We are trying to run this down. So far, it's unsubstantiated. But we've shown, I think in the past, that we will do everything in our power to establish what has happened and then consider possible steps in response," she said.