China's relations with the United States is "full of vigor and vitality," Chinese Vice President Hu Jintao said in the evening of May 2 as his six-day diplomatic mission to the United States neared its end.

Washington and Beijing are poised to grow closer economically and politically, provided both sides respect agreements and communiqués crafted since the late president Richard Nixon "opened the gate" between the two countries 30 years ago, Hu said at a banquet San Francisco Mayor Willie Brown hosted in his honor.

Hu said the array of views he exchanged this week with President George Bush and Vice President Dick Cheney left him believing that, while US-China relations have "not always been smooth," there is enough understanding to work through problems.

"Both sides have taken on to resolve differences and improve relations," Hu told more than 500 people at the Hilton Hotel in downtown San Francisco.

"Tomorrow, I leave for China. I take with me the confidence that in the years to come, US-China relations will flourish and prosper."

Hu predicted that the coming phase in the relationship between the two great nations would bring "opportunities for growth and severe tests."

China will seize entrance into the World Trade Organization as a chance to deepen political and economic reforms and "open itself wider to the world," Hu said.

Within the next five years, he added, the value of goods imported to China is expected to reach 1.5 trillion dollars.

Brown praised Hu as an energetic and optimistic leader who will "make the world a better place for all who live in it."

Nearly a third of San Francisco County residents are of Asian ancestry, and San Francisco has long had a sister city relationship with Shanghai.

A San Francisco Ballet prima ballerina born in Shanghai joined Brown in presenting Hu a golden key to the city, which the mayor said made Hu an honorary resident.

"Let us work hard to insure the bright future of China-US relations," Hu said, lifting his wine glass to Brown's in a toast.

Dining tables were draped with red cloth illuminated from below and centerpieces were lighted globes with gold stars marking San Francisco and Shanghai.

Hu wished San Francisco luck in winning the 2012 Olympic games.

Brown and former secretary of state George Schultz flanked Hu at a long center table shared by Hu's wife, Chinese and American diplomats and business leaders.

On May 3, Hu is expected to address local Chinese community leaders at a luncheon at the Hilton before returning to China on an early afternoon flight out of San Francisco International Airport.