An influential U.S. senator warned Thursday that U.S.-Russia relations will be “strained for some time” but urged immediate efforts to extend a nuclear arms-control agreement that expires in December. “The foundation of the U.S.-Russian strategic relationship is at risk of collapsing in less than nine months,” Senator Richard Lugar, the senior Republican on the Foreign Relations Committee, said in a statement. Lugar was referring to the 1991 Strategic Arms Reduction Treaty (START), which committed Washington and Moscow to significantly reduce their nuclear arsenals, including cutting missiles to a maximum of 1,600 and warheads to 6,000. “We should carefully set priorities. Solidifying the START verification regime must be the primary focus,” Lugar said as the committee opened a hearing on efforts to improve U.S.-Russia relations. Earlier this month U.S. Secretary of State Hillary Clinton said after meeting with her Russian counterpart, Sergei Lavrov, that both countries agreed renewing the treaty was “of the highest priority.”