The United States is continuing to look for creative ways to reduce Russia's oil revenue and lower global demand for oil creates an opportunity for more sanctions, Treasury Secretary Janet Yellen said on Wednesday.

The United States has been constantly tightening sanctions on Russia over the Ukraine war and Russia has invested a lot of its own fleet of ships to avoid a Western oil price cap, she said in an interview with Bloomberg Television.

Yellen said Washington's overall aim has been to impair Russia's ability to continue conducting the war by taking a variety of steps, but it has been focused from the beginning on Russia's oil revenue.

"Now what's unusual about this moment is that the oil market seems to be well supplied," she said. "Prices are relatively low. Global demand is down, and there really has been an increase in supply," Yellen said.

"So the global oil market is softer, and that creates, possibly, an opportunity to take some further action."

The Treasury Department on Tuesday said it transferred the $20 billion U.S. portion of a $50 billion G7 loan for Ukraine to a World Bank intermediary fund for economic and financial aid to the war-torn country.

The department said the disbursement made good on its October commitment to match the European Union's commitment to provide $20 billion in aid backed by frozen Russian sovereign assets alongside smaller loans from Britain, Canada and Japan to help the Eastern European nation fight Russia's invasion.

(Reporting by David Lawder and Doina Chiacu; Editing by Alexandra Hudson)