The United States is watching North Korea’s recent maneuvers “very closely,” and will “take care of it” if the country makes more advances in its nuclear weapons program, U.S. President Donald Trump told reporters at the White House on Monday.

Trump’s remarks come one day after his top envoy for the DPRK, Stephen Biegun, arrived in Seoul for a series of high-level meetings with his South Korean counterparts about the fate of long-stalled nuclear negotiations with Pyongyang.

Little more than two weeks now remain before North Korean leader Kim Jong Un’s self-declared year-end deadline for a deal with the U.S.