The United States on Monday described Russian President Vladimir Putin as desperate over the Ukraine conflict in meeting with North Korean leader Kim Jong Un, and renewed warnings that any arms deal could trigger US sanctions.

"Having to travel across the length of his own country to meet with an international pariah to ask for assistance in a war that he expected to win in the opening month, I would characterize it as him begging for assistance," State Department spokesman Matthew Miller told reporters.

"President Putin launched this war against Ukraine, with its full-scale aggression, with a dream of restoring the glory of the Russian Empire. That hope, that expectation of his, has failed," Miller said.

Miller said that Putin was traveling "hat in hand" to the talks expected in the coming days in the Far Eastern Russian city of Vladivostok after missing the Group of 20 summit in New Delhi due to his own "pariah" status.

"I will remind both countries that any transfer of arms from North Korea to Russia would be in violation of multiple United Nations Security Council resolutions," Miller said.

"We of course have aggressively enforced our sanctions against entities that fund Russia's war effort, and we will continue to enforce those sanctions and will not hesitate to impose new sanctions as appropriate."