The United States has warned it is considering new sanctions against Russia over its involvement in the latest fighting in Ukraine.

“We have additional tools and sanctions that we can certainly choose to put in place,” State Department spokeswoman Jen Psaki said on Thursday.

She said those options would be discussed with NATO allies.

“A military solution is not what we think is the appropriate approach so we are taking every tool that we can to see if we can reach a solution here through diplomatic means,” she added.

NATO said Thursday that at least 1,000 Russian troops were on the ground in eastern Ukraine supporting pro-Moscow separatist rebels fighting Kiev.

Ukraine’s pro-Western government has asked for urgent help after a rebel counter-offensive smashed through an army blockade around the separatist stronghold of Donetsk and threatened the port city of Mariupol.

“Our focus remains on non-lethal assistance – we have provided a range of non-lethal assistance as have a number of other countries in Europe,” Psaki said.

“We have not ruled out options. Obviously, there are a range of requests we have and that the National Security Council team can certainly consider, but I have no update or predictions for you at this point,” she said.