SEOUL—The U.S. sees no need to redeploy nuclear weapons to South Korea, a senior U.S. official said Wednesday, despite increasing pressure from some ruling-party politicians here.

"We have no plan and we have no intention to deploy U.S. tactical or other nuclear weapons in South Korea. Moreover, we don't believe that there is a military need to do so," Robert Einhorn, the State Department's special adviser for nonproliferation and arms control, said to reporters during a visit at South Korea's foreign ministry. "The...