Barack Obama has been accused of reneging on his disarmament pledges after it emerged the administration was planning to spend billions on upgrading nuclear bombs stored in Europe to make the weapons more reliable and accurate.

Under the plan, nearly 200 B61 gravity bombs stockpiled in Belgium, the Netherlands, Germany, Italy and Turkey would be given new tail fins that would turn them into guided weapons that could be delivered by stealth F35 fighter-bombers.

"This will be a significant upgrade of the US nuclear capability in Europe," said Hans Kristensen, a nuclear weapons expert at the Federation of Nuclear Scientists. "It flies directly in the face of the pledges Obama made in 2010 that he would not deploy new weapons."

In its Nuclear Posture Review in 2010, the US undertook to do reduce the role and numbers of its nuclear weapons, in part by not developing new nuclear warheads, and pledging it would not "support new military missions or provide for new military capabilities".

According to newly published budget figures, the US will spend about $10bn (£6.5bn) on a life extension programme for the B61 bombs, and another $1bn on adding controllable tail fins. Kristensen said the tail kit would give it a new mission and new capabilities, once some of the upgraded weapons were deployed as scheduled in Europe in 2019 or 2020.