WASHINGTON, June 28 (Reuters) - In a new verbal slip-up, U.S. President Joe Biden said on Wednesday that Russian President Vladimir Putin was "losing the war in Iraq" when he meant to say Ukraine.

Speaking to reporters briefly before departing the White House on a trip to Chicago, Biden was asked if Putin had been weakened by the brief uprising led by a Russian mercenary chief whose forces had been fighting against Ukraine.

"It's hard to tell really. But he's clearly losing the war in Iraq. He's losing the war at home and he has become a bit of a pariah around the world. And it's not just NATO, it's not just the European Union. It's Japan, it's 40 nations," he said.

It was the second slip-up in 24 hours. On Tuesday night, Biden corrected himself at a campaign fundraising event - referring to China when he meant India, whose prime minister, Narendra Modi, visited the White House a week ago.

"You probably saw my new best friend - the prime minister of a little country that's now the largest in the world, China - I mean, excuse me, India. India is not looking for a permanent alliance, but they're looking for some hedge against - in the region," he said.

The miscues are not unusual for the 80-year-old president.

Public opinion polling shows that a majority of Americans have concerns about Biden's age. Some 73% of respondents to an April 21-24 Reuters/Ipsos poll said that they considered Biden too old to work in government. A majority - 63% - of Democrats agreed with that statement.

Biden's doctor declared him healthy and "fit for duty" in February after a physical examination.