Sen. Joe Lieberman (ID-Conn.) made it clear Thursday that his support for the new Strategic Arms Reduction Treaty with Russia would hinge on the administration’s Nuclear Posture Review and plans for nuclear weapons modernization.

Republican sources were sending similar signals Thursday, suggesting that President Barack Obama has some work ahead of him if he is to garner the 67 Senate votes required to ratify the treaty, which he and Russian President Dmitry Medvedev signed in Prague. Lieberman, in a prepared statement issued Thursday afternoon, did not mince words.

“I have always supported the longstanding, bipartisan effort to reduce the number of nuclear weapons in the world. I believe, however, that any reductions in our nuclear stockpile must be accompanied by an appropriate modernization plan to bring our aging nuclear weapons complex, our warheads, and our delivery systems up to 21st century standards,” Lieberman said. “My vote on the START Treaty will thus depend in large measure on whether I am convinced the Administration has put forward an appropriate and adequately-funded plan to sustain and modernize the smaller nuclear stockpile it envisions.”

A Republican Senate aide said the GOP would stake out similar ground and noted that the minority was unified in this position. In December, the full Republican Conference and Lieberman sent Obama a letter informing him that their support for a new treaty would depend on the administration submitting an acceptable nuclear weapons modernization plan.

“Until that plan is presented, he won’t see support for the treaty,” the GOP Senate aide said.

Senate Minority Whip Jon Kyl (R-Ariz.) is set to play point for the Republicans on this issue. Kyl is no stranger to treaty battles, having helped to sink a nuclear test ban treaty signed by then-President Bill Clinton back in the mid-1990s.