U.S. Secretary of State Hillary Clinton has sworn in Gary Locke as the new U.S. ambassador to China.

At the State Department Monday, Clinton said the U.S. relationship with China is an “extraordinarily important one.” She said both countries are large, complex nations with different histories and political systems, but that they know the importance of working together.

Clinton said Locke, the first Chinese-American U.S. ambassador to Beijing, goes to China with a lot of work to do, and that there will be many difficult issues and challenges.

Locke said the nations have a “profoundly important and complex diplomatic, economic and strategic relationship.” He said that relationship has challenges but also holds great promise for extended cooperation and collaboration.

Locke served two terms as governor of the western U.S. state of Washington, and most recently was commerce secretary in the Obama administration. Jon Huntsman, who is seeking the U.S. Republican Party nomination for president, stepped down as the ambassador to China in April.