By Fredrik Dahl
VIENNA (Reuters) - The United States and Britain took part for the first time on Monday in an international conference on the humanitarian impact of nuclear weapons and were expected to face pressure to do more to eliminate their atomic arsenals.
The three other officially recognized nuclear weapon states -- Russia, France and China -- shunned the Dec. 8-9 meeting. Many of the 157 states taking part are critical of what they see as too slow headway on nuclear disarmament.
The conference, the third in a series which began in 2013, comes amid talk of a new Cold War between the West and Russia over the Ukraine crisis, during which President Vladimir Putin has pointedly stressed Moscow's nuclear arsenal.
Explaining its decision to come to Vienna, the United States said last month it had decided "there were real prospects for constructive engagement with conference participants", but added it would not engage in disarmament negotiations at the meeting.
Austrian Foreign Minister Sebastian Kurz said the attendance of two of the five permanent U.N. Security Council members was a "first success" of the conference, adding: "It is high time to move from words to real action."
Under the 1970 nuclear Non-Proliferation Treaty (NPT), the five recognized atomic bomb "haves" agreed to work towards eliminating their bombs, while the "have-nots" pledged not to pursue them. A treaty review conference is scheduled for 2015.
Critics say there has been more emphasis on meeting the non-proliferation goal than getting the five major powers to fulfill their part of the deal. The five argue that much progress has already been made, with stocks much lower than at any time in the past half century.
"STILL TOO MANY"
The U.S. atomic arsenal has been cut by 85 percent from its Cold War heights to 4,800 weapons, a U.S. official said last week. But, "that is still too many and we know it", said Rose Gottemoeller, under-secretary of state for arms control.
U.N. disarmament chief Angela Kane said countries without nuclear bombs were "becoming increasingly exasperated" that disarmament negotiations were not happening. It seems the weapon states "don't really see that the NPT is an obligation to disarm", she told Reuters.
Pakistan and India, which both have nuclear weapons, have not signed the NPT. They attended the Vienna talks, as did Iran, which rejects Western accusations it too wants to build a bomb.
Israel, which is believed to have the Middle East's only nuclear arsenal and is also outside the NPT, did not attend.
(Editing by Gareth Jones)