“And over the years, it will start going up, and they will be terrific,” he said.

Mr. Trump made the comments while highlighting his efforts to strike better trade and military deals with American allies. But his assertions confused both South Korean officials and the South Korean news media.

Mr. Trump also said South Korea had been paying only $500 million, or one-tenth, of the $5 billion he said was needed annually to maintain American military bases in South Korea. But South Korea says its contribution covers nearly half the total cost of such operations.

Both the United States Embassy and Foreign Minister Kang Kyung-wha of South Korea reconfirmed the 1.04 trillion won figure on Wednesday. Ms. Kang said her government needed to find out how Mr. Trump came up with different figures.

Kim Eui-kyeom, a spokesman for President Moon Jae-in, pushed back at Mr. Trump’s suggestion that South Korea would have to increase its contributions in the coming years, saying that it “shouldn’t be taken as a fait accompli.” He said the deal struck on Sunday, under which South Korea agreed to an 8 percent increase in its contribution, was valid only for this year, with the possibility of an extension for another year if both sides agreed.

This is not the first time South Koreans have been flummoxed by Mr. Trump’s claims.

In an interview aired early this month on CBS News, Mr. Trump complained about the “very expensive” costs of keeping 40,000 troops in South Korea. But American troops in South Korea number only 28,500.