U.S.-South Korean talks on sharing the cost of keeping American troops in South Korea are on track and ahead of schedule, but the U.S. side does not necessarily see a hard deadline ahead of the November U.S. election, a senior Biden administration official told Reuters.

Joint combat firing drills between South Korean and U.S. troops near the demilitarized zone separating two Koreas, in Pocheon.

The two sides named envoys this month to launch a new early round of talks for a deal to take effect in 2026. South Korean media said the aim was for an agreement before any comeback by Donald Trump, who during his presidency accused Seoul of "free-riding" on U.S. military might.

Trump demanded Seoul pay as much as $5 billion a year for the deployment of some 28,500 American troops as part of efforts to deter nuclear-armed North Korea.

The U.S. official said the talks were "very much on track and ahead of schedule."

"I can't say at this moment quite how soon they'll wrap, but we are not seeing major hurdles. And we're seeing a lot of political will on both sides," the official said, speaking on condition of anonymity.

"We're fairly confident that our incentives are aligned, and that we will get these negotiations done. So we'd like to make quick progress, but ... don't necessarily see November as a hard deadline."

South Korea began shouldering the costs of U.S. deployments, used to fund local labor, the construction of military installations and other logistics support, in the early 1990s.

The current agreement is set to expire in 2025, with negotiations on a successor pact usually held just before the end of the existing one.

During Trump's presidency, both sides had struggled for months to make progress, before reaching a deal when Seoul agreed to increase its contribution by 13.9%, the biggest annual rise in nearly two decades.

Trump is set to face off against President Joe Biden in the November election.

A senior South Korean presidential official said this week Seoul expects no fundamental shift in relations with the United States even if U.S. voters elect a new president, but hopes to make progress on defense cost-sharing talks and other issues this year.