LOS ANGELES, Oct. 11 (Xinhuanet) -- A top US space expert on Tuesday spoke highly of the launch of China's second manned spacecraft, Shenzhou VI, and called for in-depth space cooperation between the United States and China.

China's Shenzhou VI spacecraft successfully sent two astronautsi nto orbit at 9:00 a.m. Beijing time (0100GMT) on Wednesday.

"It's a demonstration. The launch of Shenzhou VI manned spacecraft clearly demonstrates China's consistent presence in space," Joan Johnson-Freese, a professor chairing the Department of National Security Studies at US Naval War College, told Xinhua.

"As to manned space exploration, China is catching up with the United States quickly," she said.

Johnson-Freese is widely acknowledged for her advocation of US space exploration. Her book "The Chinese Space Program: A Mystery Within a Maze", and dozens of research papers have made her a top US observer on China's space exploration.

Shenzhou spacecrafts are built upon China's own technologies, she said. "And in Shenzhou VI we can find a lot more technical advancements."

A member of US National Research Council and a senior advisor to US Congress on space strategy, Johnson-Freese refuted that China's manned space exploration would become a threat to the United States.

The expert also urged better and deeper cooperation between theUnited States and China in space exploration, saying it's in the interests of both nations.

"I'm a supporter of space cooperation," she said. "The space cooperation between US and China should be independent from their political disputes."

Through the cooperation, China will make more valuable contributions to world's space exploration, she said. "Recently, US and China have (had) more discussions on space issues. That's agood tendency."