Cost-sharing talks between the U.S. and South Korea broke down over U.S. President Donald Trump's demands for a fivefold funding increase, raising new questions about the stability of one of America's closest alliances.

Talks between the two on Tuesday ended abruptly, with each side blaming the other. South Korea's Foreign Ministry said it expected to discuss "an acceptable range for both counterparts" based on past cost-sharing discussions, while the chief U.S. negotiator, James DeHart, said that Seoul was "not responsive to our request for fair and equitable burden-sharing."

The move was likely to stoke concern in Tokyo, which is due to begin its own negotiations on a defense cost-sharing deal next year.