Key Sen. Joe Lieberman (I-Conn.) said he's not on-board yet with a nuclear arms reduction treaty.

Lieberman, the centrist senator who caucuses with Democrats, said he can't support the New Strategic Arms Reduction Treaty (New-START) in its current form.

"Not yet," Lieberman said at the Capitol when asked about his support for the treaty. "I'd like to be in a position to support it."

The senator, who serves as chairman of the Senate Homeland Security Committee, said he was focused on greater verification requirements within the agreement, which President Obama signed with Russian President Dmitry Medvedev earlier this year.

The treaty, which requires 67 Senate votes for ratification, has moved steadily through the Senate Foreign Relations Committee, with an eye toward bringing it to the floor soon. (Obama has said he'd like to see ratification by November.)

But Lieberman and some other Republicans have expressed reservation about the treaty and whether or not it would weaken the U.S. national security posture, putting the treaty in potential danger in the Senate.