When U.S. Defense Secretary Mark Esper rang his South Korean counterpart this week, he pressed for a deal quickly on defense cost-sharing that President Donald Trump expects will translate into much higher contributions from Seoul.

But current and former U.S. officials say privately there appears to be little hope of clinching a new agreement in the coming days, and some wonder about the coming weeks and months.

Trump, they say, already rejected what was probably Seoul's best offer ahead of its mid-April parliamentary elections — an increase of at least 13 percent from the previous accord, two of the officials said.