Obama administration officials pressed the case on Sunday talk shows for speedy Senate approval of the new START treaty with Russia on nuclear weapons, which appears imperiled because of opposition from a key Republican.

Top officials said that passage of the treaty during the lame-duck session was in the country’s national security interest because the U.S. cannot keep an eye on Russia’s nuclear weapons program.

“We do not have any inspectors verifying what Russia is doing with its nuclear arsenal,” Secretary of State Hillary Rodham Clinton said on “FOX News Sunday.”

“Well, certainly what I think is that there is a urgency with respect to ratifying this treaty that needs to be recognized,” Admiral Mike Mullen, chairman of the joint chiefs of staff, said on ABC’s “This Week.” “This is a national security issue of great significance. And the sooner we get it done, the better.”

The White House has launched an aggressive public relations campaign for approval of the treaty before the start of the next Congress, when passage will become more difficult because of the increased number of Republicans in the Senate. Passage of treaties requires two-thirds of the Senate, or 67 votes. Chances of the treaty approval in the lame duck diminished when a key Republican, Arizona Sen. Jon Kyl, said he could not support it this year because he needed more time to study the pact.

Some conservatives said they are skeptical the Russians will comply with the verification process.

But Mullen said the verification system in the new treaty is better than existed in the past. The treaty is a revised version of the 1991 pact between the two countries.

Clinton said the treaty was in line with Ronald Reagan’s statement about the relationship with Russia, which was that there was a need to “trust, but verify” with the former Soviet nation. In the past, consideration of international treaties had not only been bipartisan but nonpartisan, Clinton said. She also noted this version of the treaty was passed out of the Armed Services Committee on a strong bipartisan vote.

“We’re continuing to work with Democratic and Republican Senators,” she said.

Mullen also said he was concerned that failure to approve the treaty could hurt what he called “the emerging relationship with Russia.”

The debate over the treaty comes as the New York Times reported Sunday that North Korea may be expanding its nuclear weapons program.

Mullen said the report confirmed his long-standing concerns about the intentions of North Korea’s leader, Kim Jong Il.

“I think we have to continue to bring pressure on him specifically,” he said.