Moscow and Kazakhstan have initialled an agreement on jointly building and operating what would become Kazakhstan's only nuclear power plant, Russia's nuclear agency Rosatom said on Wednesday.

Russian and Kazakh officials initialled the draft agreement to build the plant during a visit to the energy-rich Central Asian country by Russian President Vladimir Putin on Tuesday.

The draft deal, agreed at a regional summit in the western Kazakh city of Atyrau on Tuesday, calls for the plant's size and capacity to be firmed up in a contract at a later stage.

In May, Russia and Kazakhstan had already signed a memorandum of understanding on the project saying the plant would have capacity up to 1,200 megawatts.

The two ex-Soviet countries also agreed in another memorandum this month that there was a possibility that the nuclear fuel for the plant could be produced in Kazakhstan.

Kazakhstan is the world's leading uranium producer.

The ex-Soviet state was used as a site for nuclear weapons tests by the USSR and Russia continues to lease a test range there.

It used to have a Russian-built nuclear reactor used to generate electricity and desalinate water, which closed down in 1999.

It is an energy-rich country whose sector of the Caspian Sea incorporates the massive Kashagan oil field, one of the world's largest. But it currently generates most of its electricity from coal.

Russia and Kazakhstan are members of an economic union along with Belarus that will come into force in 2015.