Gov. Bruce Rauner is among three Republican governors attending an annual summit in California hosted by billionaire conservatives Charles and David Koch — a trip that’s drawn criticism from unions and some Democratic lawmakers over its timing.

The Koch brothers, the nation’s top conservative donors, have hosted gatherings of donors and politicians over the years, but usually in private. This year’s attendees include five Republican senators, three governors and two congressmen.

The governor’s office confirmed Rauner is attending the summit in Palm Springs, California, but said he’s there to discuss policy and the state’s achievements with criminal justice reform, not politics or fundraising. An administration aide added that Rauner is also meeting with people on the West Coast to recruit tech companies to come to Illinois.

But the Illinois Federation of Teachers, which is in a longstanding war with the governor amid the state’s budget impasse, on Sunday harshly criticized Rauner for what they called “huddling” with the Koch brothers as refugees are stranded and Illinois is in “crisis.”

“Actions speak louder than words. He’s not compassionate. He’s not willing to work together,” IFT President Dan Montgomery said in a statement. “In one of our darkest hours, he’s plotting with billionaires on how to make the rich richer.”

State Sen. Daniel Biss, D-Evanston, who is considering a run for governor, also questioned why Rauner wasn’t at O’Hare International Airport on Saturday, where a President Trump executive order barring refugees and green card holders from seven Muslim-majority nations prompted 18 people to be detained.

Rauner’s staff said in a statement Sunday that the United States’ tradition of welcoming immigrants should be balanced with national security concerns, but they added the governor is “opposed to immigration bans that target any specific religion” and acknowledged “serious concerns” about Trump’s order.

“We urge swift resolution of these concerns through the courts to ensure we are a nation that is both secure and welcoming of immigrants and refugees,” Rauner spokeswoman Catherine Kelly wrote.

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The Koch network, known as the Freedom Partners Chamber of Commerce, plans to spend between $300 million and $400 million to influence politics and public policy over the next two years. Much of that money will be devoted to the organization’s nationwide grassroots organization to help educate voters and hold elected officials accountable.

The network is considered to be one of the most powerful in conservative politics, with an enormous budget and staff. The brothers largely back politicians and causes aligned with free-market views.

Rauner is seeking re-election next year but he is certainly not facing any financial hardships of his own. In December, Rauner contributed $50 million to his re-election campaign.

The Koch brothers are top contributors to the Republican Governors Association, which then contributes to candidates, including Rauner. Records show Rauner’s campaign committee received $8.75 million from the association beginning in March 2014.

“We’re just getting started,” billionaire industrialist Charles Koch said at the opening reception for the weekend conference, which attracted more than 550 donors, each willing to donate at least $100,000 each year to the various conservative political and policy groups backed by the Koch brothers.

Koch and many of his top donors refused to support Trump in the run-up to his election, raising questions about both his readiness for the job and his dedication to conservative principles. There were lingering signs of tensions as donors arrived Saturday.

Trump’s name was not mentioned by Koch — or the four other speakers — at the welcome reception. The group’s primary benefactor ignored the new administration and noted instead that his network successfully helped preserve the Republican majority in the Senate.

The Kochs and their supporters are focused on re-shaping the federal health care system and eliminating federal regulations. They sharply oppose, however, efforts by the Trump administration to interfere with free trade.

Wisconsin Gov. Scott Walker and Arizona Gov. Doug Ducey are also attending the three-day summit.

Contributing: AP