A Chinese satellite is expected to orbit Mars in 2009, thanks to an agreement the country signed with Russia on Monday.

During President Hu Jintao's current visit to Moscow, the two countries agreed to stage a joint unmanned mission to the red planet and one of its moons in two years, the China National Space Administration said Tuesday in Beijing.

The agreement represents a "milestone" in the history of space cooperation between the two neighbors, the agency said in a statement.

"It indicates the two sides have taken a key step forward to working together on a large space program."

According to the agreement, a micro-satellite developed by China will be launched along with "Phobos Explorer", the Russia spacecraft, atop a Russian rocket in 2009.

A timetable was not mentioned, but earlier Russian reports said the launch window for the 10-11 month voyage to Phobos, a Martian moon, will be October 2009.

Phobos became a satellite of Mars millions of years ago, so studying material from the asteroid will give scientists information on the origins of the solar system and of Earth, the Russian news agency RIA Novosti cited Russian Academy of Sciences member Mikhail Marov as saying.

After entering Mars' orbit, the Chinese micro-satellite will be detached from the Russian spacecraft, and probe the Martian space environment, according to the statement.

The "Phobos Explorer" spacecraft, with some equipment developed by the Hong Kong Polytechnic University, will land on the Martian moon and return to Earth with soil samples.

Monday's agreement was signed by the China National Space Administration head Sun Laiyan and the Russian Federal Space Agency chief Anatoly Perminov and witnessed by the two countries' presidents.

Last year, the Russian space chief revealed that his country would work "closely" with China on lunar exploration.

Youriy Nosenko, deputy chief of the Russian space agency, told a press conference in Beijing last November that Russia regards China as a "partner" in space exploration, and the two sides have shown interest in a lunar project.

China has started a three-stage moon exploration project, including sending a lunar orbiter some time this year, followed by a soft landing in 2012 and the return of lunar samples in another five years.