The head of Russia's space agency says that the US has rejected a Moscow proposal that the two countries join forces to explore the Moon.
"We were ready to co-operate, but for unknown reasons, the United States have said they will undertake this programme themselves," Anatoly Perminov said.
US space agency Nasa has said it plans to start work on a base on the Moon when astronauts return there in 2020.
Nasa has not commented on Mr Perminov's statement, reported by Interfax news.
Nasa and Russia's federal space agency Roskosmos have experience of working together on the International Space Station (ISS).
The construction of the ISS has relied heavily on Russian Soyuz spacecraft to ferry personnel and supplies, particularly when all US space shuttles were grounded as a result of the Columbia disaster in 2003 in which seven astronauts died.
And Mr Perminov announced that Roskosmos had signed a "contract for nearly $1bn" with Nasa to supply cargo shuttles between now and 2011 for the ISS.
Mr Perminov said that he hoped Russian and US expertise could also be pooled as part of Nasa's plan to build a permanently-occupied Moon base.
"Strange as it is, the United States is short of experts to implement the programme," Interfax quoted him as saying.
The base is likely to be built on one of the Moon's poles and will serve as a science centre and possible stepping stone for manned missions to Mars.
The US has already said it plans to build a new lunar spacecraft using funds diverted from space shuttle flights, due to be scrapped in 2010.