Rep. Seth Moulton, fresh off a visit to Ukraine, said the country is doing "incredibly well" but needs access to American aid more quickly as they brace for a tough winter ahead.

Speaking on Greater Boston, Moulton said Ukraine is defeating Russian President Vladimir Putin in his march westward. "Putin is not going to stop. He's going to keep going," Moulton said.

Despite impressive resilience and resolve on behalf of Ukrainians, Moulton said, "Make no mistake — this is an absolutely brutal war."

He said American aid has been absolutely vital, but needs to arrive faster. American support for funding the war has dwindled, but Moulton said investment now will save American lives and dollars later on if the war progresses and spills over into NATO territory.

Ukraine needs to push forward and take back more territory to get Russia in a position to negotiate, Moulton said.

Watch: ‘Putin’s not going stop’: Rep. Moulton shares his experience during recent visit to Ukraine