SINGAPORE (BLOOMBERG) - South-east Asian nations with longstanding ties with Russia that have hesitated to pick sides in the war in Ukraine are increasingly questioning the value of that relationship as the war in drags on, US State Department Counsellor Derek Chollet said.

Speaking in an interview on the sidelines of the Shangri-La Dialogue in Singapore, Mr Chollet said recent talks with Asian leaders have revealed new doubts among nations that officially maintain non-alignment in the war.

"For a lot of countries, that's not an easy decision to make because they may have relationships with Russia, and for many, many years," he said without specifying the countries.

"But I found that many of those countries are questioning that future."

Delegates from the United States led by Secretary of Defence Lloyd Austin are in Singapore this weekend as part of a push to convince the region of their vision of a free and open Asia-Pacific.

While Mr Chollet said it is too early to tell whether countries will shift their stance on the war, they have been put off by the economic cost as well as the underwhelming performance of Russia's military.

"This is a country that's even more isolated in the world," he said. "There's higher cost to being a partner. Its economy is going to be in the toilet, so we are making clear what we see as the cost of that partnership."