The United States has agreed to maintain wartime control of South Korean troops in the event of an attack by North Korea for the foreseeable future, delaying the transfer of authority to Seoul that had been scheduled for 2015.

The agreement has been discussed for more than a year and comes at the request of Seoul. There is no longer a deadline for the transfer.

Defense Secretary Chuck Hagel made the announcement Thursday alongside South Korea Defense Minister Han Min Koo at the Pentagon.

Hagel, in a visit to South Korea last October, said the timing of the transfer would be based on military conditions.

The U.S. has tried for years to wean South Korea off its dependence on the American military by setting a target date for the transfer.