Russia and the United States agreed Wednesday to cooperate on a NASA-led project to build the first lunar space station, part of a long-term project to send humans to Mars. The US space agency said earlier this year that it was exploring a programme called the Deep Space Gateway, a multi-stage project to push further into the solar system. The project envisages building a crew-tended spaceport in lunar orbit that would serve as a "gateway to deep space and the lunar surface," NASA has said. An international base for lunar exploration for humans and robots and a stopover for spacecraft is a leading contender to succeed the $100 billion International Space Station (ISS), the world's largest space project to date. On Wednesday, the Russian space agency Roscosmos and NASA said they had signed a cooperation agreement at an astronautical congress in Adelaide. NASA said the agreement reflected the two agencies' common vision for human exploration. "While the deep space gateway is still in concept formulation, NASA is pleased to see growing international interest in moving into cislunar space as the next step for advancing human space exploration,"  Robert Lightfoot, acting administrator at NASA headquarters in Washington, was quoted as saying. The Russians and Americans would cooperate to build the systems needed to organise scientific missions in lunar orbit and to the surface of the Moon, Roscosmos said. The Russian space agency added the partners intended "to develop international technical standards which will be used later, in particular to create a space station in lunar orbit." Russia, the United States and other participants agreed it was important to work using unified standards to avoid future problems in space, Igor Komarov, Roscosmos's general director, said in televised remarks, citing the trials of Sandra Bullock's astronaut heroine in sci-fi thriller "Gravity". "Roscosmos and NASA have already agreed on standards for a docking unit of the future station," the Russian space agency said. "Taking into account the country's extensive experience in developing docking units, the station's future elements -- as well as standards for life-support systems -- will be created using Russian designs." NASA said it planned to expand human presence into the solar system using its new deep space exploration transportation systems, the Space Launch System rocket and Orion spacecraft.   - 'Better to fly together' -   Russia and the United States also discussed using Moscow's Proton-M and Angara rockets as well as other spacecraft to help create the infrastructure of the lunar spaceport, the Russian statement said, adding that the main works were slated to begin in the mid-2020s. Space exploration is one of the few areas where international cooperation between Russia and the US has not been wrecked by tensions over Ukraine, Syria and elsewhere. Russia and the US work side by side on the ISS, which has been orbiting Earth since 1998. "We understand that we are key players and we have to work on these missions together,"  Komarov said. "The station will be a serious platform for future research," he said. Experts hailed the announcement as a symbolic beginning of US-Russian joint work on deep space exploration. "It's better to fly together to the Moon than think who will strike first," Igor Lisov, an editor at Space News, an industry journal, told AFP. He said Russia had a lot to contribute, given the country's expertise and experience. "We are offering carriers for flights to a lunar orbiting station, we are offering our docking units or their components," he said, adding Russia had vast experience in creating life-support systems. "That is a rather significant contribution." Sending the first man into space in 1961 and launching the first Sputnik satellite four years earlier are among key accomplishments of the Soviet space programme and remain a major source of national pride in Russia.