The "ambassadors" promised to be "courteous, well-informed and respectful" and "smile often" when they swore in at an opening ceremony of the US Pavilion Monday morning.

"It's gonna be stressful but happy," said Micah Phelps, a public relations major from Utah who is among the first group of 80 student ambassadors that will work at the Expo for three months.

Like all other "ambassadors", Phelps speaks fluent Chinese and knows a lot about China.

Phelps' parents worked in China in their younger days and his mother is the first Chinese language teacher in Utah. "My younger sister, who my parents adopted from China almost 10 years ago, is the only one who doesn't speak Chinese in my family."

The US Pavilion shows films starring a number of Americans -- including Barack Obama and Kobe Bryant -- greeting the audience in Chinese and showcasing imagination and perseverance in preserving the earth and improving community.

"I enjoyed the films very much," said Jing Zefeng, 12. "I was particularly impressed by the American children's fantastic ideas, such as to fuel cars with fruit juice and travel wherever you want on the cloud... I had similar ideas when I was, say, about five years old."

Jing, a fifth-grader at a primary school in Shenzhen, a boom city in Guangdong Province, said the Expo was for him a window on the world. "I hope to meet more people and grow up to be a global citizen."

The US Pavilion is receiving an average 25,000 visitors daily and except to draw a total of 6 million in six months, says Commissioner General Jose Villarreal.

"I had expected to see more high-tech stuff here," said Xiao Jiutang from Guangdong after touring the pavilion. "It's a little disappointing to see a display of sponsors. The American films are quite impressive, though."

Far from the American venue, on the southeastern end of the Expo park, the national pavilion of the Democratic People's Republic of Korea is another major attraction for the Chinese, who are eager to have a glimpse of its close neighbor and buy stamp albums commemorating the two country's traditional friendship.

The DPRK, which has attended an Expo for the first time, has taken "Paradise for the People" as the theme of its pavilion.

"It's unique but still similar to Chinese culture," said Zhang Weiguo, a 50-something visitor from the neighboring Zhejiang Province, who waited for at least 20 minutes to buy five albums. "The stamps with handshakes between former Chinese and DPRK leaders are good collections and make ideal gifts for friends and relatives back home."

A total of 204,000 people visited the Expo on Saturday, the opening day, and 221,800 visitors toured the park on Sunday, said Hong Hao, director-general of the Bureau of Shanghai World Expo Coordination.