US President Barack Obama (C) announces that Commerce Secretary Gary Locke (R) will become the new US Ambassador to China as Secretary of State Hillary Clinton looks on in the Diplomatic Room at the White House in Washington March 9, 2011. Locke will replace Jon Huntsman who will step down on April 30. [Photo/Agencies]

WASHINGTON - US President Barack Obama on Wednesday nominated as his top envoy to Beijing Commerce Secretary Gary Locke, the first Chinese-American to serve in that diplomatically and commercially important assignment.

"When he's in Beijing, I know that American companies will be able to count on him to represent their interests in front of China's top leaders," Obama said as he announced Locke's nomination.

Related readings:  Locke nomination shows focus on China ties  Obama to name Locke as new US ambassador to China

Underscoring the critical nature of the relationship between the US and China, Obama was flanked by Secretary of State Hillary Clinton at the ceremony in the White House Diplomatic Room.

Locke drew on his compelling family history in accepting the nomination. His grandfather first came to America to work as a houseboy in a Washington home in exchange for English lessons. His father, who also was born in China and moved to the US as a teenager, died in January.

"I know that if he were still alive, it would be one of his proudest moments to see his son named as the United States ambassador to his ancestral homeland," said Locke, as his wife and three young children looked on.

If confirmed by the Senate, Locke would replace Ambassador Jon Huntsman, who leaves China in April. Huntsman, the former Republican governor of Utah, has overtly signaled his intention to run against Obama in the 2012 election, a move that has irritated many in the White House.

The president lauded Huntsman as an "outstanding advocate for this administration" _ praise the White House knows full well could hurt Huntsman with Republican primary voters.

Locke, a soft-spoken 61-year-old, is popular in China, say those who have traveled with him to China. During his more than 20 trips to China over the past 20 years, Locke has built a relationship with many government officials and China's business community.

The US-China relationship stretches well beyond economics. The US needs Chinese support on a range of foreign policy matters, from nuclear standoffs with Iran to peacekeeping efforts in Sudan.

The White House said there was no timetable for replacing Locke, who is the first member of Obama's cabinet to leave the administration.