MOSCOW, Feb 4 (Reuters) - Russia said on Wednesday it was open to diplomacy on nuclear security but would resolutely counter any new threats, after what it called a mistaken and regrettable decision by the United States not to stick to the missile and warhead limits of the expiring New START nuclear treaty.
The 2010 New START treaty, which limits the size of the Russian and U.S. strategic nuclear arsenals, expires at the end of Wednesday, and the two sides have not held any talks on a replacement.
Security experts have voiced concern that the treaty's lapse could pave the way for a new arms race in which China would also be a major player.
(Reporting by Maxim Rodionov; Editing by Mark Trevelyan)
