WASHINGTON (NYTIMES) - The Trump administration, scrambling to avoid a rift with an ally, has told South Korea it is open to holding preliminary talks with North Korea, according to two senior administration officials and a spokesman for the South Korean president, Moon Jae-in.

The decision, which came after Vice President Mike Pence attended the Winter Olympics in Pyeongchang, South Korea, and met President Moon, reflects how thoroughly the diplomatic channel between the North and South has upended the administration's calculations.

For months, the White House has rejected the idea of meeting with North Korea unless it took measurable steps toward giving up its nuclear stockpile and curbing its provocative behaviour. Now, though, with Moon determined to engage with the North, these officials said the administration has decided on a course correction.

The decision was a victory for South Korea. "The United States, too, looks positively at South-North Korean dialogue and has expressed its willingness to start dialogue with the North," Mr Moon said Tuesday, according to his spokesman, Kim Eui-kyeom.

US officials were more guarded, saying they were open to talks but not a full-fledged negotiation.

The United States, they said, would reiterate its demands that North Korea make concessions and did not plan to offer any in return. As of now, there are no plans to cancel or further delay joint military exercises by the United States and South Korea, scheduled for after the Olympic Games.

Still, the tactical shift by the White House opens the door to an unpredictable new phase in the crisis over North Korea. It also shows how the North Korean leader, Kim Jong Un, has been able to use the Olympics to pursue a thaw with a receptive counterpart in the South.

President Donald Trump himself has oscillated between a get-tough approach and a dealmaker's belief that he can sit down with Kim and work out an agreement. Some of his advisers, like Secretary of State Rex Tillerson, favour engagement; others, like the national security adviser, Lt-Gen. H.R. McMaster, have pushed for more pressure, backed by the threat of military action.

Reports that Washington and Seoul had reached an understanding on the possibility of dialogue appeared in the news media after the vice president's departure on Saturday, but South Korean officials would not confirm them until Tuesday.

Dialogue with the North has been used by successive US administrations as a carrot - paired with the stick of sanctions - in the hopes of getting the isolated nation to end its nuclear weapons program. But the Trump administration has long resisted that approach, saying it would not be drawn into a negotiation like that of the Clinton administration in 1994, which resulted in a deal North Korea later broke.

Just six months ago, Trump described Moon's overtures to the North as "appeasement". When Tillerson said in December that the United States was willing to hold a "meeting without precondition", the White House dismissed his comments as premature.

But in an interview with The Washington Post after he left South Korea, Pence suggested that the United States was open to a meeting, even indicating that it would enter talks without preconditions.

"The maximum pressure campaign is going to continue and intensify," Pence said of the punishing sanctions imposed on the North by the United Nations. "But if you want to talk, we'll talk."

Agreeing to talks before the North Koreans have demonstrated a willingness to dismantle their weapons program would be a subtle but potentially significant shift in Washington's approach - and a win for Moon.

When Pence and Moon met last week, the allies apparently found common ground: They would agree to talks without set rules, but they would continue to use sanctions as leverage.

"President Moon and I reflected last night on the need to do something fundamentally different," Pence told reporters Friday after meeting with the South Korean leader.

The allies, he said, would demand "at the outset of any new dialogue or negotiations" that North Korea "put denuclearization on the table and take concrete steps with the world community to dismantle, permanently and irreversibly, their nuclear and ballistic missile programs." "Then, and only then, will the world community consider negotiating and making changes in the sanctions regime that's placed on them today," Pence said.

At the same time that Pence was in South Korea, Kim Yo Jong, the sister and special envoy of North Korean leader Kim Jong Un, also visited the South as part of an Olympic delegation. She extended an invitation from her brother to Moon for a summit meeting in North Korea.

Moon, who invited athletes from the North to participate in the Olympics - where they marched with South Korean athletes under a unified Korean flag during the opening ceremony - has seen the games as an important step toward promoting peace on the Korean Peninsula.

Deciphering the Trump administration's signals on North Korea is tricky, given the president's unpredictability. Trump has repeatedly contradicted Tillerson when he has floated diplomatic openings. But Pence, officials point out, received his marching orders from Trump shortly before he left for Asia, and he was unlikely to deviate from them.

The White House has been relieved by the lull in North Korea's nuclear and missile tests, even as it has watched the emerging détente warily. North Korea has not conducted any major weapons tests since Nov 29, when it launched an intercontinental ballistic missile powerful enough to reach the mainland United States.

Even if talks start between North Korea and the United States, the gap between the countries remains wide. Analysts predicted that North Korea would use any future talks with Washington to be accepted as a nuclear power and win large economic concessions, in return for agreeing not to advance its nuclear weapons program any further.

North Korea has said it would not bargain away its weapons and would only discuss mutual arms reduction - a vow US intelligence agencies take seriously. The CIA has assessed that no amount of pressure will lead Kim to give up his arsenal.

In testimony before the Senate on Tuesday, the director of national intelligence, Dan Coats, said, North Korea "has repeatedly stated that it does not intend to negotiate its nuclear weapons and missiles away because the regime views nuclear weapons are critical to its security." Kim, he added, "probably sees nuclear ICBMs as leverage to achieve his long-term strategic ambition to end Seoul's alliance with Washington and to eventually dominate the peninsula."