WASHINGTON (Reuters) - Among some U.S. officials, congressional aides, analysts and others who track North Korea, there was a sigh of relief on Thursday as President Donald Trump headed home empty handed from his talks with North Korean leader Kim Jong Un in Vietnam.

U.S. President Donald Trump boards Air Force One to continue his return to Washington from his summit meeting with North Korea's Kim Jong Un in Vietnam after a refueling stop at Elmendorf Air Force Base in Anchorage, Alaska, U.S., February 28, 2019. REUTERS/Leah Millis

Trump said he walked away from a deal because of Kim’s demands to lift all U.S.-led sanctions on North Korea in return for the denuclearization of its Yongbyon atomic complex but not others that the United States knows about.

In contrast, North Korea’s foreign minister said Pyongyang offered to dismantle Yongbyon in return for a partial lifting of sanctions as a step toward better relations between the nations, technically still at war because the 1950-53 Korean War ended in an armistice rather than a peace treaty.

Before the summit, there were hints Washington was open to declaring an end to the war, some sanctions relief, and opening of liaison offices, a first step toward diplomatic ties, if the North reined in its nuclear program.

The fear of many in the U.S. national security establishment was that Trump would give up too much in return for too little and they were pleased that did not happen. There was still concern in Washington, however, about what the summit’s collapse would mean for future nuclear diplomacy with North Korea.

Former U.S. Deputy Secretary of State Richard Armitage said the summit’s failure had eased fears that Trump, anxious to claim a foreign policy success, might have made an agreement that dispelled the North Korean nuclear-armed missile threat to the continental United States, but not the threat of its shorter-range missiles to U.S. regional allies, such as Japan.

“The general feeling was that all President Trump wants is a scalp to hang on the wall, like he did with calling the Singapore nothing-burger a great victory,” said Armitage, referring to Trump’s first summit with Kim in June 2018.

That produced a vague statement of Kim’s pledge to work toward denuclearization of the Korean peninsula but little progress followed.

Trump’s defenders have long said he had no intention of giving ground to Kim at their second meeting in Hanoi this week without major North Korean concessions.

They said Trump planned to use the rapport he claims with Kim and negotiating skills honed as a real estate developer to secure the best possible deal despite skepticism from critics who question whether he is up to speed on the main issues.

Mark Dubowitz of the Foundation for Defense of Democracies think tank rejected criticism that Trump came up empty, tweeting: “Actually walking away from a bad proposed deal is exactly what we’d expect from a competent deal-maker.”

It had appeared Trump was moving toward offering Pyongyang concessions on a peace deal, sanctions and liaison offices in return for “promises to make promises to move toward (nuclear) disablement and dismantlement,” a congressional aide said on condition of anonymity. “There is a certain sigh of relief in that respect.”

Nuclear analysts estimate North Korea may have a nuclear arsenal of 20 to 60 weapons which, if mated with intercontinental ballistic missiles it has developed, could threaten the U.S. mainland.

The collapse of the summit leaves Kim in possession of that arsenal though Trump said the North Korean leader had agreed to maintain his moratorium on nuclear and ballistic missile tests.

The United States has long resisted offering the North a formal end to the war regarding this as a concession that should not be made until Pyongyang abandoned its nuclear arms. U.S. intelligence officials have said there is no sign North Korea would ever give up its entire arsenal of nuclear weapons, which Kim’s ruling family sees as vital to its survival.

An end to the war could also have spurred demands from North Korea for the United States to withdraw some of its 28,500 troops from South Korea, where they serve as a trip wire to deter a North Korean invasion.

Trump, who has questioned the value of keeping the troops there, made clear before the summit that removing them was off the table, another source of relief for those who believe their withdrawal could embolden the North and endanger the South.

One of the ironies that experts pointed out was that in failure, Trump may actually have had a success.

It may also have been a victory for hawkish White House national security adviser John Bolton, who has pressed for Washington to maintain its “maximum pressure” sanctions campaign intact while demanding Pyongyang’s full denuclearization.

Even Adam Schiff, the Democrat who chairs the House Intelligence Committee and is one of Trump’s main critics in Congress, offered qualified praise.

“President Trump’s decision to walk away from the summit with North Korea without an agreement was preferable to making a bad deal,” he said.