The US envoy to North Korea, Sung Kim, arrived in Seoul, the South Korean capital, on Monday.
His visit is for talks with senior South Korean officials.
It comes after an unprecedented series of missile tests by Pyongyang.
Since the start of the year, North Korea has conducted more than a dozen test launches, including launching a long-range intercontinental ballistic missile (ICBM) for the first time since 2017. This weekend end, Pyongyang, the North Korean capital, tested a weapon system intended to increase the effectiveness of its nuclear weapons.
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During this five-day visit, the American envoy from Pyongyang is to meet his South Korean counterpart, Noh Kyu-duk, as well as senior officials of the country.
His arrival comes at a time when South Korea and the United States have started annual military exercises.
They must last nine days.
These joint maneuvers, which still anger Pyongyang, have been reduced in recent years, the outgoing president, Moon Jae-in, favoring a policy of dialogue with the North.
"This exercise is defensive command post training using computer simulation, and there is no real military maneuver training," the South Korean Joint Chiefs of Staff said on Sunday.
The United States has 28,500 soldiers stationed in the South, in order to protect the country against its neighbor.
The United States ready for dialogue at any time and unconditionally
Pyongyang had suspended nuclear and long-range missile testing when North Korean leader Kim Jong Un and then-US President Donald Trump began high-profile talks, which broke down in 2019. The talks are since stalled.
Upon his arrival, the senior US official said he was in Seoul to continue "close cooperation" on developments in North Korea, according to the Yonhap news agency.
Sung Kim said that Washington, the American capital, is open to dialogue with Pyongyang at any time and without preconditions.
But this offer has so far been rejected by Kim Jong Un.
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