North Korea said Monday it is willing to reopen denuclearization talks with the United States in late September, but warned that Washington needs to come up with fresh ideas or risks jeopardizing the negotiations.

Talks between Pyongyang and Washington have stalemated since a second summit in February between U.S. President Donald Trump and North Korean leader Kim Jong Un in Hanoi ended abruptly without a deal. Trump rejected Kim's demand for relief from the debilitating U.S. economic sanctions in return for partial denuclearization.

The two leaders agreed at a short meeting in June at the Demilitarized Zone separating North and South Korea to restart staff level talks but they have yet to start.

In the new overture, Choe Son Hui, the North's vice foreign minister, said in a statement carried by the official Korean Central News Agency, "We are willing to sit face-to-face with the U.S. around late September at a time and place that we can agree on."

But Choe said the United States has to produce an "acceptable calculation" or risk the end of the talks, apparently a statement aimed at pushing the United States toward making concessions to North Korea, such as on the economic sanctions.

There was no immediate response from the U.S. on the North Korean statement, although Washington has expressed a willingness to resume talks and has set a goal for the denuclearization of the Korean peninsula by the end of Trump's first term in office in January 2021.

At their first summit more than a year ago in Singapore, Trump and Kim adopted a statement calling for the "complete denuclearization of the Korean peninsula."

Trump returned from Singapore to Washington, saying, "There is no longer a Nuclear Threat from North Korea. Sleep well tonight!"

But nothing has occurred since then to indicate that North Korea has been dismantling its nuclear arsenal, and to the contrary, a United Nations report last week said the North's development of nuclear warheads has not stopped.

North Korea has launched a series of missile tests since late July in protest of joint military exercises between South Korea and the U.S. Trump has dismissed the importance of the tests, but other key U.S. officials have voiced concern that the missiles could be used to attack South Korea and U.S. troops stationed there.

"We're disappointed that he is continuing to conduct these short-range tests. We wish that he would stop that. But our mission set at the State Department is very clear: to get back to the (negotiating) table," Secretary of State Mike Pompeo told the ABC News show "This Week" on Sunday.