Russia has indefinitely postponed the program to develop the Tupolev PAK DA strategic stealth bomber in favor of renewed production of the cheaper and less complex Tupolev Tu-160M2 White Swan, a supersonic, variable-sweep wing heavy strategic bomber.

Russian state-owned media outlets said Russia's Ministry of Defense postponed work on PAK DA to renew serial production on the latest iteration of the Tu-160M.  The Tu-160M entered service with the Russian Aerospace Force in 2005.

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Only 27 of these variable-wing bombers were built, however. The main mission of the Tu-160M is to deliver nuclear weapons onto enemy targets.

The Russian Aerospace Forces currently operates some 15 Tu-160M supersonic strategic bombers, of which 11 are fit for frontline service.

The Tu-160 was upgraded following its entry into service. The upgrade gave the bomber the ability to launch the Kh-101 and Kh-555 -- both of which are nuclear missiles.

Kh-55 is a subsonic air-launched cruise missile with a range of up to 2,500 km. The weapon is launched exclusively from bomber aircraft such as the Tu-160. Kh-101 is a semi-stealthy nuclear missile designed for air launch. It has a range of up to 10,000 km.

Work on developing PAK DA began in 2009 and Russia initially planned to begin testing the bomber between 2019 and 2020. Restarting serial production for the Tupolev Tu-160 delayed the program and that delay has now led to the program's postponement until production of the new Tu-160 is completed.

The Russian Aerospace Forces are expected to receive at least 50 of the new variable-wing aircraft after serial production begins in 2023. The upgraded version, the Tu-160M2, will feature new weaponry, new engines and improved electronics

The PAK DA program was almost cancelled in 2012, partly as a result of funding shortfalls.

Russian military experts also say there is serious debate going on in military and government circles about the wisdom of developing PAK DA since the Tu-160 can meet the demands of being the aerial leg of Russia's nuclear triad.

"That's why no one is in a hurry to create the new strategic bomber until there is a real technical breakthrough," said Pavel Bulat, director of the International Mechanics and Energy Systems Laboratory at the University of Information Technologies.

Bulat noted the Americans have been making new bombers for 20 to 30 years. This process takes too much time "because neither they nor we have a real need for such planes. Their old B-52s, just like our Tu-160s, meet all the challenges of the nuclear triad," according to Bulat.