When it comes to his philanthropic and humanitarian work in Africa, Bono doesn’t choose political sides. He’s forged solid alliances with Democrats and Republicans alike, but Donald Trump, should he win the White House, is gonna be a tough one, the U2 frontman said last week.

“The whole point of [Bono’s charity] ONE is it’s bi-partisan and this would be the biggest challenge for me, by far,” Bono told a Canadian online media outlet ahead of his visit last week to Montreal to speak at a conference hosted by Prime Minister Justin Trudeau to fundraise for AIDS prevention programs in underdeveloped countries.

“But it’s not going to change my respect for the Republican Party or anything. It’s really his hijacking of it.”

Trump’s GOP bona fides are questionable, says Bono. “I’m not sure he’s a Republican. I have huge respect for the GOP and the party of Abraham Lincoln. Some of my best friends in development are Republicans in the United States,” he offered.

Trump is in “special category” status, according to Bono, who is alarmed by the rhetoric Trump has spouted since announcing his run for office last summer.

“This jingoism and this hate-filled speech is just not helpful,” he said. “I’m just figuring out live what I think about him, so I can’t give you a definitive answer.”

Read more: Bono sought favorable access to Hillary through Clinton Foundation claims GOP

Speaking on Trump again earlier this week, the U2 frontman compared the governments of Britain and Ireland to the US, which he claimed is different for being based on an idea.

“Look, America is like the best idea the world ever came up with,” Bono claimed in a “CBS This Morning” interview on Tuesday.

“But Donald Trump is potentially the worst idea that ever happened to America. Potentially.

“That idea is bound up in justice and equality for all — equality and justice for all, you know? I think he’s hijacked the party, and I think he’s trying to hijack the idea of America. And I think it’s bigger than all of us. I think it’s — this is really dangerous.”

Bono was a guest at President Bill Clinton’s 70th birthday celebration at the Rainbow Room in New York on Friday evening, and flew up to Montreal the next day for Trudeau’s gathering which also included Bill Gates.

Bono said that Canada has always been a leader in the global fight against AIDS. "It's just great to see Canada leading on this. You've always been ahead of the curve in realizing we can do more if the international community works together and subsuming your ego into the grand plan,” he told conference attendees.

The Irish star returned to New York this week to attend the twelfth and final annual Clinton Global Initiative conference to be hosted by the former president. Bono has taken part in panel discussions in previous years of the conference and earlier this year was linked with a batch of Hillary Clinton emails criticized for revealing that certain donors to the Clinton Foundation requested favorable access to the then-Secretary of State. Bono, a long-time friend of the Clinton Foundation, is believed to have requested high-level help broadcasting a live link to the International Space Station during concerts.”