U.S. Ambassador to the U.N. Nikki Haley smiles while President Donald Trump speaks before a working lunch with U.N. Security Council member nations in the State Dining Room of the White House April 24, 2017 in Washington, D.C. | Brendan Smialowski/AFP via Getty Images Trump disses the United Nations as an ‘underperformer’ U.S. president also praises his U.N. Ambassador Nikki Haley.

WASHINGTON — With the ambassadors to the United Nations Security Council gathered around him in the White House on Monday, President Donald Trump labeled the U.N. “an underperformer” and appeared to both heavily praise and jokingly jab at his U.N. ambassador, Nikki Haley.

"I also want to say to you that I have long felt that the United Nations is an underperformer, but has tremendous potential,” Trump said, according to the press pool that was ushered into the White House’s state dining room for the beginning of his working lunch with the Security Council ambassadors. “We must also take a close look at the U.N. budget. Costs have absolutely gone out of control."

Trump called himself “a budget person” but suggested that “if you do a good job at the United Nations,” his concern about the U.N.’s spending might diminish to some extent.

While Trump heaped praise on Haley, one of the loudest voices on foreign policy from his administration thus far, he also jokingly threatened to replace her if the other ambassadors in the room did not get along with her.

“I want to thank Ambassador Nikki Haley for her outstanding leadership and for acting as my personal envoy on the Security Council. She is doing a good job. Now, does everybody like Nikki?” Trump said. “Otherwise she could be easily replaced, right? No, we won't do that. I promise you we won’t do that. She’s doing a fantastic job.”

He also accused the U.N. of being unwilling to tackle the world’s most challenging problems, telling the ambassadors that “the United Nations doesn't like taking on certain problems,” naming Syria’s use of chemical weapons as an example. Trump called North Korea “a big problem” and said “people have put blinders on for decades.”

Both Syria and North Korea have been the beneficiary of protection from permanent Security Council members who have shielded the two repressive states with their veto power. The regime of Syrian dictator Bashar Assad, widely blamed for chemical weapon attacks inside its own borders amid a years-long civil war, has been protected from U.N. consequence by Russia, which maintains one of its few foreign military bases in Syria and is a longtime ally of Assad’s.

And China has long protected North Korea, wary of destabilizing the region and of any conflict that might lead to the downfall of North Korean dictator Kim Jong Un, a scenario in which South Korea would likely absorb the North and put a U.S. ally and partner right on China’s border.