MOSCOW, Aug 16 (Reuters) - Russia's lunar spacecraft entered the moon's orbit on Wednesday, a major step towards the country's ambition of being the first to land on the moon's south pole in the search for frozen water.

The Luna-25 entered the moon's orbit at 11:57 a.m. (0857 GMT), Russia's space corporate Roskosmos said.

Luna-25 will circle the moon, the earth's only natural satellite, for around 5 days, then change course for a soft landing on the lunar south pole planned for Aug. 21.

India's Chandrayaan-3 entered the moon's orbit earlier this month ahead of a planned touchdown on the south pole of the moon later this month.

The Luna-25, which is roughly the size of a small car, will aim to operate for a year on the south pole, where scientists at NASA and other space agencies in recent years have detected traces of frozen water in the craters.

The presence of water on the moon has implications for major space powers, potentially allowing longer human sojourns on the planet that would enable the mining of lunar resources.

No Russian spacecraft has entered lunar orbit since Luna-24, the Soviet Union's 1976 moon mission, according to Anatoly Zak, the creator and publisher of www.RussianSpaceWeb.com which tracks Russian space programmes.

"Entering lunar orbit is absolutely critical for the success of this project," Zak told Reuters. "This is a first for the post-Soviet period."

"Some are calling this the second lunar race so it is very important for Russia to resume this programme. Luna-25 is not just one mission - it is part of a much broader Russian strategy that stretches 10 years into the future."