Sens. Dick Lugar (R-Ind.) and Ben Nelson (D-Neb.) on Tuesday signaled some willingness to support the Strategic Arms Reduction Treaty President Barack Obama signed with Russia, a good sign for the administration as it seeks to build support for the agreement.

Lugar, the ranking member on the Foreign Relations Committee, said he agrees with his Republican colleagues that ratification of the arms treaty hinges upon the Obama administration moving forward with an acceptable nuclear weapons modernization program. But Lugar appeared more flexible on the implementation of this plan than Senate Minority Whip Jon Kyl (R-Ariz.), the GOP point man on the issue.

And also unlike Kyl, Lugar said he views the Nuclear Posture Review document on U.S. nuclear strategy as a separate issue. The Obama administration has made some changes to how and when the U.S. would use nuclear weapons, and Kyl and other defense hawks, such as Sens. John McCain (R-Ariz.) and Joe Lieberman (ID-Conn.), have taken exception.

“I’m generally in favor of ratification,” Lugar said, adding that he is “sympathetic” to the idea that START ratification, which requires an ultra-supermajority of 67 votes, be linked to nuclear weapons modernization.

“I favor the modernization program that many Republican Senators have called for,” he said.

Nelson, chairman of the Armed Services Subcommittee on Strategic Forces, is scheduled to hold a hearing Wednesday on the operations status of existing nuclear stockpiles. Nelson declined to give START a full-throated endorsement, but he also didn’t voice the same type of reservations that Lieberman has expressed in recent days.

Nelson also declined to link backing of the treaty to the implementation of an acceptable nuclear weapons modernization program. Additionally, Nelson indicated that he was not likely to have trouble with the Nuclear Posture Review.

“At this point in time I haven’t made up my mind on it. But I’m not looking for reasons not to support it, either,” Nelson said Tuesday, when asked if he was prepared to vote to ratify START.

National Nuclear Security Administration Administrator Thomas D’Agostino, a top Obama administration official on the subject of nuclear weapons modernization, is scheduled to testify Wednesday afternoon at Nelson’s Strategic Forces Subcommittee hearing.