WASHINGTON (AP):  The United States and South Korea have reached agreement in principle on a new arrangement for sharing the cost of the American troop presence, which is intended as a bulwark against the threat of North Korean aggression.

The State Department's Bureau of Political-Military Affairs said the deal includes a negotiated increase in Seoul's share of the cost, but it provided no details.

The Bureau wrote on Twitter that the agreement, if finalised, would reaffirm the US-South Korean treaty alliance as the linchpin of peace, security and prosperity for Northeast Asia.

The negotiations had broken down during the Trump administration over a US demand that Seoul pay five times what it previously had paid.

The State Department said in a statement that the increase in the South's share of the cost was meaningful."

The U.S. keeps about 28,000 troops in South Korea.

The Wall Street Journal, which was first to report the agreement, said it would last through 2025.

In its statement, the State Department said: America's alliances are a tremendous source of our strength. This development reflects the Biden-Harris administration's commitment to reinvigorating and modernising our democratic alliances around the word to advance our shared security and prosperity.