"When the leader comes to the floor and says that our national security is being driven by politics, we really need to step back for a moment and calm down and think for a moment about what is at stake," the Massachusetts Democrat said. He later added: "I mean is there no shame ever with respect to the arguments that are made sometimes on the floor of the United States Senate."
State Department spokesman P.J. Crowley said Republican lawmakers had legitimate concerns, but "we believe that we've answered those concerns." So at this point, he said, objections "are more about politics than substance."
Senior Democrats pushed toward a possible decisive vote on Tuesday to cut off debate and set the stage for a final vote later in the week. Republicans and Democrats were discussing amendments to the accompanying resolution — not the treaty — that would address GOP concerns about missile defense and build support for the agreement.
"It's going to be a real slog, house by house combat if you will, but I think we'll be there," Sen. Chuck Schumer, D-N.Y., told ABC's "Good Morning America" on Monday. Schumer also said longtime Mississippi Sen. Thad Cochran was on board, but when questioned later in the day, the Republican told reporters he didn't want to talk about his vote.
Democrats expect to get 57 votes from their caucus, with Sen. Ron Wyden, D-Ore., absent due to cancer surgery on Monday. Five Republican senators — Richard Lugar of Indiana, Olympia Snowe and Susan Collins of Maine, George Voinovich of Ohio and Brown — have said they back the treaty while four others — Robert Bennett of Utah, Judd Gregg of New Hampshire, Tennessee's Bob Corker and Isakson — said they were leaning toward approval.
Corker said he has received several calls from Biden.
In Russia, Foreign Minister Sergey Lavrov warned against any changes to the treaty.
"I can only underline the fact that (the treaty) that was developed on a strict basis of parity, in our view corresponds fully to the national interests of Russia and the U.S.A.," Lavrov told Russia's Interfax news agency. "It cannot be opened up and become the subject of new negotiations."
The treaty specifically would limit each country's strategic nuclear warheads to 1,550, down from the current ceiling of 2,200. It would also establish a system for monitoring and verification. U.S. weapons inspections ended a year ago with the expiration of a 1991 treaty.
Associated Press writers Ben Feller and Mark S. Smith contributed to this report.
- ACT scores, 2015: A breakdown of each state,...
- The 25 most educated cities in America: Where...
- Poll: Utahns would take Donald Trump over...
- Fired reporter kills 2 former co-workers on...
- KUTV back on DISH Network; KSL still dark on...
- Trump says he's proud he booted Univision's...
- Walmart to cease sales of semiautomatic rifles
- GOP presidential candidate Rand Paul to hold...
- Poll: Utahns would take Donald Trump... 75
- Trump starts new media feud with... 36
- What keeps teachers from staying in the... 34
- GOP presidential candidate Jeb Bush has... 28
- USC's Steve Sarkisian apologizes for... 17
- Trump says he's proud he booted... 16
- US stocks pare losses after 1,000-point... 15
- Fired reporter kills 2 former... 15