SEOUL, South Korea — The U.S. special envoy for North Korea reaffirmed Friday that Washington is ready to hold talks with the North, South Korea's government said, as North Korea escalates its calls for the U.S. to make new proposals to resolve the impasse in their nuclear diplomacy.

Stephen Biegun's reported comments come a day before President Trump is to visit South Korea for two days.

Talks between Mr. Trump and North Korean leader Kim Jong Un in Vietnam in February ended early without any agreement. But during their first summit in Singapore last year, Kim pledged to work toward complete denuclearization of the Korean Peninsula, and the two leaders agreed to improve bilateral relations and build lasting peace on the peninsula.

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During a visit to Seoul on Friday, Biegun told his South Korean counterpart that Washington is prepared for "constructive" talks with North Korea to implement the commitments made during the Singapore summit "simultaneously and in parallel," according to Seoul's Foreign Ministry.

Before the Vietnam summit, Biegun made similar remarks, saying that Washington had told North Korean officials that it was prepared to pursue "simultaneously and in parallel" the commitments Trump and Kim made in Singapore.

The Vietnam summit, however, collapsed after Mr. Trump rejected Kim's calls for major sanctions relief in return for dismantling his main Yongbyon nuclear complex, a partial denuclearization step.

Biegun's comments Friday were seen as an offer for talks on what concessions the United States could offer instead of sanctions relief in return for the dismantling of the nuclear complex, said analyst Cho Han Bum at Seoul's Korea Institute for National Unification.

"The U.S. doesn't intend to lift the sanctions while the only (denuclearization) step North Korea wants to take now is Yongbyon's dismantling," Cho said. "Their (ideas) are coming into conflict with each other."

South Korean President Moon Jae-in said earlier this week that U.S. and North Korean officials were holding "behind-the-scene talks" to try to arrange a third summit between Trump and Kim. Secretary of State Mike Pompeo said Sunday the U.S. was prepared to resume talks with North Korea "at a moment's notice" if the North signaled it wanted discussions about denuclearization.

North Korea's Foreign Ministry slammed the United States on Thursday for talking repeatedly "like a parrot" about a resumption of talks without mapping out measures to salvage the nuclear diplomacy. The ministry on Wednesday accused the United States of using sanctions to "bring us to our knees."

On Friday, North Korea's state media criticized downsized military drills between the United States and South Korea planned in August, describing them as an "intolerable" provocation that raises questions about whether the two countries are truly committed to peace on the peninsula.

Following the Singapore summit, Mr. Trump suspended large-scale annual U.S. military exercises with South Korea to facilitate the nuclear talks. While Washington and Seoul have replaced those war games with smaller exercises, North Korea has called for a complete halt of joint drills, which it views as rehearsals for an invasion.

The drills are "an act to create the atmosphere of confrontation and danger of war again," the North's official Korean Central News Agency said.