Senate Homeland Security and Governmental Affairs Chairman Joe Lieberman (ID-Conn.) said Sunday that President Barack Obama would face an uphill battle to win the 67 votes he needs to ratify the new Strategic Arms Reduction Treaty with Russia.

“Based on some conversations I’ve had over this break with some of my colleagues, I don’t believe that there will be 67 votes to ratify the START treaty unless the administration does two things,” Lieberman said on Fox News Sunday.

Lieberman, who is withholding his own vote for ratification until his terms are met, said the administration must commit to modernizing U.S. stockpiles. He also said he wants assurances that Russia would not pull out of the treaty if the U.S. presses ahead with plans to build a missile defense shield in Europe, despite comments to that effect from Russian President Dmitry Medvedev when he and Obama signed the treaty April 8 in Prague. The Senate must ratify the treaty, and several Republicans have already said they want certain conditions met before agreeing to do so.

“We need that defense to protect our allies and ourselves from Iran,” Lieberman said.

Unless his concerns are addressed, Lieberman — who often sides with Republicans on foreign affairs — said he would be “really hesitant” to vote for the treaty, which will be in the news again this week as world leaders travel to Washington for a nuclear security summit.

Without Lieberman’s vote, Obama would need the support of nine Republicans — and all of the other members of the 59-Senator Democratic Conference — to win ratification.

But Republican Conference Chairman Lamar Alexander (Tenn.) said on the same program that — as far as he and other Senate Republicans were concerned — the issue was off the table until at least next year.

“There’s not a chance the treaty will be approved this year,” Alexander said, noting that ratification of an earlier START treaty took more than a year and that the Senate would also be dealing in the coming weeks with a Supreme Court confirmation as well as with legislation to help the economy. “This is a treaty for next year.”

It was too early to predict GOP support for the treaty, Alexander said. He called the agreement “a modest step” to reduce nuclear weapons, but said the Senate needed to “take plenty of time” to answer questions about the treaty’s implications.

In December, the full Republican Conference and Lieberman sent Obama a letter saying that their support for a new treaty would depend on the administration submitting an acceptable nuclear weapons modernization plan.