WASHINGTON (AFP) - Russia's plans to renew its military and nuclear arsenal are not cause for alarm, the US Defence Department said on Tuesday. Russia was "perfectly entitled to a robust self-defence," Press Secretary Geoff Morrell told a news conference. "I have not heard any alarm in this building about any proposed Russian build-up of its military," he said. Defence Secretary Robert Gates has spoken previously about how Russia's aging population means Moscow will have trouble recruiting enough young soldiers and will likely reduce its large military force, Morrell said. The US and Russian militaries had forged a positive working relationship and the top US military officer, Admiral Mike Mullen, was in regular talks with his Russian counterpart, the Press Secretary said. "As long as we have a good dialogue and a good understanding of what we are both developing our militaries for, I don't see that it poses a problem or a threat that we should be concerned with," Morrell said.