This weekend's news that an United Nations arms embargo on Iran could be lifted over time may turn the ongoing nuclear talks with that nation "on their head" in the last hours before an agreement is reached, retired Gen. Michael Hayden said Monday.

"Our premise for the negotiation was if not forgiving the Iranians for a vast amount of bad activity, at least ignoring it and isolating it down not just to the nuclear program but to the nuclear enrichment program," the former National Security Agency and CIA director told MSNBC's "Morning Joe" program. "That's the only way we thought we could get a deal from the Iranians."

However, now Iran wants the outcome of any deal reached to "back up to include all those other things they claimed were never on the table. It's stunning," Hayden said.

Story continues below video.

Over the weekend, negotiators reached an agreement to lift the embargo over time,  Bloomberg News on Sunday reported, quoting an unidentified source at the Vienna talks.

The U.N. Security Council is still drafting a resolution to address the embargo, the person told Bloomberg. That resolution will call for the embargo to be lifted over time, but not immediately, the source said.

Ian Bremmer, president and founder of Eurasia Group, a political risk research and consulting firm, told the program that he believes there are several countries in Europe that will be "strongly in favor" of lifting the embargo, but Russia is particularly interested.

"The Russians came out publicly and said the arms embargo would need to be removed very early because, of course, the Iranians are critical to fighting ISIS on the ground," said Bremmer, referring to the Islamic State jihadist group by its acronym.

"The real reason, of course, the Russians are supporting it is because they want to sell a bunch of arms to the Iranians," Bremmer said. "But the point is that that's the first time we've seen the Russians split from the rest of the negotiators on the Iran issue. That made America's negotiating position weaker."

And if the deal falls apart, that will be bad news for the United States, he continued, as it will be "very hard to maintain the sanctions."

"I think the question has to be whether it's a relatively bad deal that gets done or whether it's a deal that falls apart and then they do that anyway and we lose international sanctions," said Bremmer. "I don't like either option but if you're forced to choose one, there are lots of benefits for the U.S."

Hayden, meanwhile, said that Iran is under U.N. sanctions because it has been instructed to stop enriching uranium.

Further, he called Russia a "frontier of concern," but doesn't agree that it's a rising power.

"The things that constitute Russian strength today are actually the things from the 20th century — nuclear weapons, conventional forces," Hayden said. "Putin is doing this with a pair of sevens in his hand."

But Bremmer believes that Russia has the ability and likelihood to "overplay that lousy hand," and that the United States underestimates the country's dangers in the near term. However, over the long term, the real danger is China, he said.

Related Stories:

• Diplomats: Iran Deal Announcement Planned Monday
• Decision Day at Iran Talks Edges Closer With Report of Agreement