Sen. Elizabeth Warren (D-MA) Chip Somodevilla | Getty Images

U.S. Sen. Elizabeth Warren says chaos in the Trump administration is harming its ability to formulate coherent policy toward North Korea's nuclear program and other important issues in Asia. Vacancies in the foreign service are undermining Washington's ability to advance U.S interests, Warren told reporters in Beijing on Saturday. U.S. allies, while still supportive, are "searching for information" about U.S. intentions in Asia, the Massachusetts Democrat said. "This has been a chaotic foreign policy in the region, and that makes it hard to keep the allies that we need to accomplish our objectives closely stitched-in," Warren said.

We told ourselves a happy-faced story that never fit with the facts, and now ... the United States cannot avoid facing a very different reality with China. Elizabeth Warren U.S. senator

Warren also visited South Korea and Japan during her trip to Asia. She said President Donald Trump's agreement to meet with North Korean leader Kim Jong Un was "rash," in the absence of Pyongyang's commitment to take "any steps at all to indicate that they were serious about denuclearization." On China, Warren said the U.S. needs to acknowledge Beijing's growing power and influence and continue to emphasize the importance of human rights within the relationship. "I understand that our relationship with China is complex," Warren said. "There are areas where we have mutual interests and where we will work together to try to accomplish our shared goals. But there are also areas where we are vigorous competitors and do not have shared interests." Warren said the idea that China would more smoothly integrate with the rest of the world based on its economic growth and open markets "has been proven wrong." "And the United States is now trying to recalibrate that relationship," she said.

'Happy-faced story'