"They're not clarifying. He did another Terri Schiavo diagnosis from a one-hour tape," Kerry, the party's 2004 presidential nominee, said Wednesday of the Tennessee Republican.
On Monday, Frist said the war against Taliban guerrillas can never be won militarily and that he favored bringing "people who call themselves Taliban" into the government.
The remarks drew immediate criticism from Democrats. They argued Frist was waving the white flag of surrender to the Taliban, who harbored the al-Qaida organization blamed for the Sept. 11 terrorist attacks.
A Frist spokeswoman later said the senator believes Afghan tribesmen at risk of being lost to the Taliban should be brought into the government, not Taliban fighters themselves.
Kerry, mentioned as a possible 2008 presidential candidate, was campaigning in New Hampshire for state Senate candidate Beth Roth. Frist also is considered a White House hopeful.
Frist, a former heart surgeon, took a leading role last year in the fight to get Schiavo's feeding tube reinserted. He later was criticized for relying on a video to question her doctors' diagnosis that Schiavo was in a permanent vegetative state.
Kerry said Frist's Taliban comments sound like claims by the Bush administration about progress being made in Iraq, despite differing reports from those directly involved. The Massachusetts senator said he requested a private briefing with CIA officials earlier this week.
"I will tell you their outlook was bleak. It was completely different from what the administration is saying publicly, and they told me that is what they are saying to the administration today," Kerry said.
He added: "We need an administration that tells America the truth. We don't need a cut-and-run policy in Afghanistan where the real war on terror is and a stay-and-lose policy in Iraq."