At a Monday rally in Winston-Salem, North Carolina, Donald Trump doubled down on his previous controversial remarks regarding American support for NATO allies.

In an interview with The New York Times last week, Trump hesitated to commit to a defense of Baltic states in the case of Russian aggression, saying that it would depend on whether or not those NATO allies had “fulfilled their obligations” to the United States.

On Monday night, however, Trump offered an even more explicit ultimatum to NATO allies.

“I want them to pay,” he said. “They don’t pay us what they should be paying! We lose on everything. Folks, we lose on everything.”

He went on to criticize former Secretary of State Hillary Clinton’s foreign policy record: “She makes it impossible to negotiate. She’s not a negotiator. She’s a fool.”

“We have to walk,” Trump added. “Within two days they’re calling back! Get back over here, we’ll pay you whatever the hell you want.”

“They will pay us if the right person asks,” he said. “That’s the way it works, folks. That’s the way it works.”

Trump’s initial comments on NATO drew rebuttals from Republican officials, including Senate Majority Leader Mitch McConnell (R-KY) and House Speaker Paul Ryan (R-WI). John Bolton, former ambassador to the United Nations under President George W. Bush, criticized Trump’s stance as “an open invitation to Vladimir Putin” and said that he hoped that “whoever advised Mr. Trump on this rethinks it.”

The Clinton campaign was also quick to respond to Trump’s suggestions.

“The President is supposed to be the leader of the free world,” senior policy advisor Jake Sullivan said in a statement. “Donald Trump apparently doesn’t even believe in the free world.” He went on to say that it was “fair to assume that Vladimir Putin is rooting for a Trump presidency.”