"The formal signing of the handover of the Yury Dolgoruky boat to the Defense Ministry will take place in September," the source said.

Previously, the navy had said the boat would enter service in July, and then August.

The boat has completed a range of sea trials including a firing of a Bulava ballistic missile in December 2011.

Its sister ship, the Alexander Nevsky, will carry out a further Bulava test launch in November "as part of its state trials," he said.

The Borey class will become the mainstay of the Russian Navy's strategic nuclear deterrent force, replacing older Project 667 (NATO Delta 4) boats. The class will consist of eight boats, all armed with Bulava missiles.

Meanwhile, the head of the fleet, Admiral Viktor Chirkov, said the Project 885 Yasen class hunter-killer submarine Severodvinsk may also enter service by the end of this year.

“Yasen is undergoing tests in accordance with the program. We hope it will raise the flag this year,” he said.

Several Russian media have recently claimed that the boat’s entry into service will be delayed until 2013 due to problems with its nuclear power plant. Its maker United Shipbuilding Corporation, has insisted the boat will enter service on schedule and there are no problems with it.