Yusuf Islam Jokes About Struggle Getting Into U.S. at Sean Penn's CORE Event

Yusuf Islam -- formerly known as Cat Stevens -- apparently had a tough time getting into the U.S. for Sean Penn's annual pre-Globes gala ... but it's unclear what the problem was.

The iconic British singer-songwriter was one of the performers at Penn's CORE charity event Saturday night, which raises money for disaster relief efforts in Haiti and other countries across the Caribbean every year ahead of the Golden Globes.

While introducing Yusuf, Penn noted he almost wasn't permitted to come. He doesn't elaborate beyond that, and Yusuf went on to play a beautiful set in front of folks like Julia Roberts, Anderson Cooper, Casey Affleck, Jamie Foxx, Mike Myers, Keegan Michael Key, Bonnie Hunt, Allison Williams, Larry David, Connie Britton, Ben Stiller ... and other stars in attendance.

However, based on Yusuf's history with the United States -- he was literally banned from entering the country between '04 and '06 for alleged ties to terrorist efforts, which was later found to be bogus -- it's possible his past gave him issues with U.S. Customs ... especially under the Trump administration.

Speaking of Trump ... Penn later joked that he'd applied to be Trump's new Chief of Staff in light of General John Kelly stepping down last month. Classic dry humor from SP here.