New Delhi, Nov. 29: A secretive project for the transfer of a Russian nuclear submarine to the Indian Navy has got delayed after New Delhi complained that Moscow had not trained Indian officers and sailors adequately for the task of operating it.

The Akula-II class, 8,140-tonne submarine, Nerpa, was to be delivered to the Indian Navy by December.

The Indian Navy, whose “silent arm” of submarines is fast depleting, had posted nearly 100 officers and sailors to the Amur shipyard in Siberia, where the Nerpa was built and tested, for more than a year.

Nuclear submarines can stay under water for much longer periods than the conventional diesel-electric submarines in the Indian Navy’s fleet. India has coveted nuclear submarines for decades, largely because of China’s expanding fleet.

Now the Indian Navy has concluded that its crew in Russia have not been trained well enough to “operationalise” the submarine after the transfer. The submarine is now likely to be accepted only in the middle of next year.

While the Indian defence establishment is miffed with the Russians for inordinate delays in several projects, it is also acutely aware that it cannot source such strategic co-operation from any other country.

This is the second time that the navy will be leasing a nuclear submarine from Russia after the first, the INS Chakra, was returned in 1991 after being in service in India for 10 years. In 2004, India and Russia had signed an agreement (about which officials do not talk in public) that would allow the Nerpa, which is likely to be re-christened INS Chakra, to be with India for 10 years till 2020 under a $650-million programme.

The agreement envisaged that Russia would not only physically sail the submarine to India but would also train the Indian Navy to operate it. Since its last experience with the INS Chakra, the Indian Navy’s trained personnel have almost all retired.

Also, the technology of nuclear submarines has undergone a change over the years, necessitating a fresh set of skills to operate them. The Indian Navy was intending to train its officers and sailors on the Nerpa till its own nuclear submarine, the INS Arihant, built with help from the Russians, is operationally ready.

The Arihant was “launched” in 2009 in the naval dockyard in Visakhapatnam but sea trials are yet to begin after its reactors were integrated. It is expected to be operationally ready only in 2013.

The Nerpa has had its share of misfortune. An accident killed 20 Russian sailors while the submarine was being tried in the Sea of Japan. The repairs cost more than $60 million. The accident and the repairs caused the first delay and now the delivery has been re-scheduled.