By Veronica Stracqualursi, CNN

(CNN) -- President Donald Trump on Wednesday appeared to threaten to withdraw US troops from South Korea if he can't get a better trade deal with Seoul.

In a fundraising speech in Missouri, Trump told donors South Korea had become rich but that American politicians never negotiated better deals, according to audio obtained by The Washington Post and confirmed to CNN by an attendee.

"We have a very big trade deficit with them, and we protect them," Trump said. "We lose money on trade, and we lose money on the military."

"We have right now 32,000 soldiers on the border between North and South Korea. Let's see what happens," Trump said.

The President went on to argue, "Our allies care about themselves. They don't care about us."

South Korea declined Thursday to respond to Trump's reported remarks.

"We're not in a position to be able to make comments every time President Trump makes remarks," Trade Ministry spokeswoman Seo Jeeyeon said.

The Blue House, the office of South Korea's president, simply said, "No comment."

The report on Trump's remarks comes hours before South Korea's foreign minister arrives in Washington to discuss the proposed face-to-face meeting between Trump and North Korean leader Kim Jong Un.