A former U.S. ambassador warned on Sunday that Russian President Vladimir Putin may have convinced President Donald Trump to accept a terrible offer during their summit in Anchorage, Alaska, last week.

Putin and Trump met on August 15 to negotiate an end to the three-and-a-half-year-long war in Ukraine. Ahead of the meeting, Trump threatened that there would be "very severe consequences" for Russia if it did not agree to a ceasefire during the summit. However, Trump emerged from the meeting saying that a ceasefire was not immediately necessary. He added that Russia agreed to allow Europe and the U.S. to offer Ukraine security guarantees.

The move set off alarm bells for Daniel Fried, a former ambassador to Poland and a senior fellow at The Atlantic Council.

Fried joined CNN's Frederika Whitfield to discuss the summit on Sunday's "CNN Newsroom."

"If they mean it, that's a big deal," Fried said of Russia accepting security guarantees for Ukraine.

Fried also cautioned that Russia has a long history of making offers that are "shiny on the outside, and poison on the inside."

He added that allowing Russia to have a say in Ukraine's security guarantees is one example of a deal that looks good, but may not be in practice.

"If they're part of a security guarantee, then it's no guarantee," Fried said.

The former ambassador also issued a warning to the Trump administration as they continue to negotiate with Putin.

"They need to be very careful not to be hoodwinked by Putin or agree to something that looks shiny and isn't," Fried said.

Watch the entire clip below or by clicking here.