The office will be open five days a week, with duty officers on standby on weekends, officials said. Personnel from both Koreas will live at the compound and be on call around the clock.

The office is in a four-story building within what used to be a factory park. The two Koreas jointly ran that park, which was established during an earlier period of warmth in their off-and-on relationship, until the South shut it down in 2016 amid rising tensions over the North’s nuclear arms program.

An agreement to open the new office was first reached in April, when President Moon Jae-in of South Korea and the North’s leader, Kim Jong-un, held their first summit meeting. They originally planned to open it in late August, but the date was pushed back after President Trump canceled a trip to Pyongyang by his secretary of state, citing a lack of progress in denuclearization talks with the North.

South Korea has dismissed concerns that it is opening up to the North too quickly, and that it should insist on more concrete steps toward denuclearization in return. Mr. Moon argues that improving inter-Korean ties will encourage, not deter, the denuclearization of the Korean Peninsula. This month he sent envoys to North Korea, who reported that Mr. Kim wanted denuclearization before the end of Mr. Trump’s current term, if he were offered the right incentives.

Mr. Moon plans to travel to Pyongyang on Tuesday for his third summit meeting with Mr. Kim. Mr. Moon hopes to help restart the stalled talks between Pyongyang and Washington.

The two Korean leaders also plan to follow up on their April agreement to ease military tensions along the inter-Korean border. At their April meeting, Mr. Moon also offered help with the modernization of the North’s decrepit railways and highways, as an incentive for the North to abandon nuclear arms.

But Mr. Moon reaffirmed this week that inter-Korean ties, including major joint economic projects, could advance only after the North denuclearizes and the United Nations lifts sanctions.