WASHINGTON, Sept 30 (Reuters) - The United States and Russia said in a joint statement on Thursday that they had held "intensive and substantive" talks in their second meeting within a framework that is aimed at easing tensions between the world"s largest nuclear weapons powers. The two countries have agreed to set up two working groups, which will convene ahead of a third plenary meeting. A date for the third gathering was not provided. U.S. President Joe Biden and Russian President Vladimir Putin, whose countries hold 90% of the world"s nuclear weapons, agreed at a June summit in Geneva to embark on an integrated bilateral "Strategic Stability Dialogue" to lay the groundwork for future arms control and risk reduction measures. Armed with mandates from their leaders, delegations from the two nations restarted talks in July, the first time in nearly a year that the two had held so-called strategic stability talks amid frictions over a range of issues, including arms control. During the second meeting held on Thursday in Geneva, the delegations headed by U.S. Deputy Secretary of State Wendy Sherman and Russia"s Deputy Foreign Minister Sergei Ryabkov agreed the working groups would focus on principles and objectives for future arms control and capabilities and actions with strategic effects. A senior U.S. administration official told reporters that Washington thought it was "a very productive meeting." "Today the discussion was very interactive and broad-based, and we think we were able to cover a variety of issues," the administration official said, declining to provide specifics. "I think this was a good building-on of the meeting that we had in July and both delegations really engaging in a detailed and dynamic exchange," the official added.