COLORADO SPRINGS — Charles Koch on Sunday forcefully shot down the possibility that he would support Democratic presidential nominee Hillary Clinton in this year’s White House race, calling such an idea “blood libel.”

“The first thing I want to do is correct a rumor that the media keeps stimulating, and that is that I’m probably going to support Hillary,” Koch told a gathering of 400 donors to his political network assembled here for a weekend retreat. “That is a blood libel,” he added to loud applause, comparing the notion to false accusations throughout history that Jews killed Christian children for ritualistic purposes.

“At this point, I can’t support either candidate,” Koch said, drawing scattered applause throughout the ballroom of the Broadmoor hotel. “But I certainly am not going to support Hillary.”

Koch’s remarks come as he has been under pressure from fellow donors to engage the network he has helped build on behalf of GOP presidential nominee Donald Trump. Koch has refused to do so, but he sought this weekend to reassure those worried about comments he made in April, when he suggested it was “possible” that another Clinton in the White House would be better than a Republican.

Top Koch officials also announced this weekend that network-backed groups plan to invoke Clinton in campaigns they are running in support of GOP Senate candidates, the closest the organization has edged toward the 2016 White House contest. But they made it clear that they would not be running an explicit effort to try to defeat Clinton.

The Washington Post and other news outlets were invited to cover portions of the weekend gathering on the condition that they do not name donors in attendance without their permission.

On Sunday, Koch said the network’s priorities would be to shape policy in Congress and support conservative leaders at the state level.

“To address the current political crisis, our first objective is to stop the worst federal policies, regardless of who is the next president,” Koch said. “And we’ve got to remember that Republican presidents advance a lot of bad policies, just like Democrats.”

He said the network’s first priority is “to preserve the country’s financial future and to eliminate corporate welfare. But since it appears that neither presidential candidate is likely to support us in these efforts, we are focused on maximizing the number of principled leaders in House and Senate who will, and giving grass-roots activists the tools to hold elected officials accountable.”