On Thursday, Republican Speaker of the House Paul Ryan — the most senior member of the U.S. House of Representatives — told CNN that he could not currently support presumptive Republican nominee Donald Trump.

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"I'm just not ready to do that at this point. I'm not there right now," Ryan told CNN's Jake Tapper.

In the past, Ryan has repeatedly said that he'd support the party's nominee, so his statement is surprising.

Ryan explained that the "bulk" of the effort to unify the party should come from Trump, as CNN reported. Here's how Ryan explained that:

"And so, I think what is necessary to make this work, for this to unify, is to actually take our principles and advance them. And that's what we want to see. Saying we're unified doesn't in and of itself unify us, but actually taking the principles that we all believe in, showing that there's a dedication to those, and running a principled campaign that Republicans can be proud about and that can actually appeal to a majority of Americans -- that, to me, is what it takes to unify this party.""

After the interview, CNN's Dana Bash called Ryan's move a "seismic event."

Earlier this week, other Republican leaders, including Republican Party Chair Reince Priebus and Senate Majority Leader Mitch McConnell, have encouraged the party to rally around Trump. But many other Republicans have openly disavowed him.

Ryan maintained that he might support Trump later on.

Ryan did not rule out supporting Trump at some point, saying "we've got a ways to go from here to there." The speaker, however, was vague about what exactly Trump would have to do to win Ryan's support.

It didn't take long for Trump to respond. On Thursday afternoon, he released a statement saying essentially the same thing — that he was "not ready to support Speaker Ryan's agenda" but hadn't closed the door entirely, according to CNN.

"Perhaps in the future we can work together and come to an agreement about what is best for the American people," Trump said. "They have been treated so badly for so long that it is about time for politicians to put them first!"

You can watch the interview with Ryan here:

This story, first posted on Thursday at 2:13 PST was updated at 3:17 PST to include a response Trump issued in a statement reported by CNN.