The United States urged North Korea to return to stalled denuclearization talks during an open debate at the U.N. Security Council on Wednesday, saying it is prepared to be "flexible" in the process while warning against continued provocative acts.

"We have not asked North Korea to do everything before we do anything. The United States is prepared to be flexible in how we approach this matter," U.S. Ambassador to the United Nations Kelly Craft said.

"But we cannot do this alone. North Korea must make this difficult but bold decision to work with us," she said.

At the same time, Craft warned of "deeply troubling indications" that Pyongyang intends to continue provoking a response through actions such as further test-firings of short-range ballistic missiles.

"These ballistic missile tests, no matter their range, undermine regional security and stability, and are a clear violation of U.N. Security Council resolutions," she said.

"These actions also risk closing the door on this opportunity to find a better way for the future," Craft added.

The latest gathering was proposed by the United States, which holds the rotating chair of the Security Council this month.

On Thursday, North Korea reacted sharply to the U.N. meeting, with an unnamed spokesman for the country's Foreign Ministry saying, "We are ready to take a countermeasure corresponding to anything that the U.S. opts for."

"We will never overlook such stance of the U.S. which played a leading role in an open UNSC meeting discussing the issue of the DPRK in a bid to incite the atmosphere of pressurizing it at this sensitive time," the spokesman said in a statement carried by state-run media.

DPRK is the acronym for North Korea's official name, the Democratic People's Republic of Korea.

With the administration of U.S. President Donald Trump shying away from joining recent multilateral statements condemning North Korea's activities, the decision to convene the council on the issue signals a policy shift, stoking speculation that Washington is toughening its stance toward Pyongyang.

But the Security Council session, which was fully open to media, underscored difficulties the world body faces in dealing with the matter.

China and Russia, two veto-wielding permanent members that typically favor a conciliatory approach toward North Korea, argued for the Security Council to ease sanctions on Pyongyang in support of the U.S.-North Korea dialogue.

It is imperative for the council to "make necessary adjustments to the sanctions measures" on North Korea to assist the talks between the United States and North Korea, Chinese Ambassador to the United Nations Zhang Jun said.

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Russian Ambassador Vassily Nebenzia pushed for North Korea to be encouraged to cooperate "by responding to what it has already done, as it expects some kind of positive reaction from us."

Japanese Ambassador Kimihiro Ishikane said North Korea's ballistic missile launches are "a serious challenge not only to Japan but to the entire international community."

It is important to dismantle "all of North Korea's weapons of mass destruction and ballistic missiles of all ranges in a complete, verifiable and irreversible manner" in accordance with U.N. resolutions, he said.

Trump, who apparently wants a deal with North Korea to boost his 2020 re-election bid, has downplayed the significance of Pyongyang's short-range ballistic missile launches, which are considered a threat to U.S. allies Japan and South Korea.

Trump said Saturday that he would be "surprised" if North Korea acted in a hostile manner despite rising tensions over the denuclearization talks.

North Korea's official Korean Central News Agency reported Monday a statement by a senior official that security threats to the United States will increase if the country ignores a year-end deadline set by Pyongyang.

At the first-ever summit between North Korean and United States leaders, in June 2018 in Singapore, Trump promised Kim Jong Un security guarantees in return for "complete" denuclearization of the Korean Peninsula.

But negotiations for concrete steps hit a snag. At their summit in Hanoi in February this year, the two leaders fell short of bridging the gap between Washington's denuclearization demands and Pyongyang's calls for sanctions relief.

The United States and North Korea held working-level talks in Stockholm in October, but the North Korean delegation walked away saying the negotiations had broken down.