* Obama cites importance of U.S. envoy to China post

* Huntsman, a Republican, was ambassador to Singapore (Adds details on Huntsman, meeting with Obama)

By Matt Spetalnick and Emily Kaiser

WASHINGTON, May 16 (Reuters) - U.S. President Barack Obama on Saturday named the Republican governor of Utah to be the next U.S. ambassador to China, a pivotal post in relations between the United States and a major emerging economic power.

Jon Huntsman Jr., 49, a Mandarin-speaking former U.S. trade official with deep personal and family business ties to China, takes on a delicate diplomatic role with a vital trading partner and one of the biggest sources of financing for the growing pile of U.S. government debt.

"This ambassadorship is as important as any in the world because the United States will best be able to deal effectively with the global challenges of the 21st century by working in concert with China," Obama said at a White House ceremony with Huntsman at his side.

But Obama also used his nomination of Huntsman, a former ambassador to Singapore who was co-chairman of Senator John McCain's presidential campaign and has been mentioned as a potential Republican presidential candidate in 2012, to send a message to China's communist leadership.

"Improved relations with China will require candor and open discussion about those issues where we don't always agree, such as human rights and democracy and free speech, and will require that each of our nations play by the rules in open and honest competition," Obama said.

Huntsman is the son of billionaire philanthropist Jon Huntsman, and his family founded chemical company Huntsman Corp, which has operations in China, including a factory in Shanghai. One of Huntsman's seven children, daughter Gracie Mei, was adopted from China.