The United States and Russia on Thursday announced a seven-year extension of their nuclear security cooperation agreement, US deputy energy secretary Daniel Poneman said.

Extending the pact, first signed in 1995, will allow the former Cold War rivals to prevent "dangerous nuclear equipment and materials from falling into the wrong hands," Poneman said in a statement.

Under the agreement, US and Russian officials try to prevent nuclear theft and terrorism by securing material at its source.

It includes surveillance of 73 Russian nuclear warhead sites, 37 Russian nuclear material sites and 13 non-Russian nuclear material sites.