Secretary of State John Kerry discounted an assessment that Pyongyang might be ready to launch a nuclear warhead. Anne Gearan is traveling with him and joins us from Seoul. (The Washington Post)

Secretary of State John F. Kerry warned North Korea’s young leader Friday that his country would lose any military showdown with the United States, and sought to play down a U.S. intelligence report that North Korea is now capable of delivering a nuclear-armed missile.

The dual signals from Kerry were part of a broader effort by the Obama administration to force North Korea to back away from its increasingly bellicose rhetoric, while also assuaging the concerns of allies and the American public.

Speaking in the South Korean capital, Kerry pledged strong support for that country as well as Japan against threats from Pyongyang, saying that its leader, Kim Jong Un, “needs to understand, as I think he probably does, what the outcome of the conflict would be.”

The tone of that reference to U.S. military power seemed designed to reinforce a message the administration has also delivered more explicitly in recent weeks by repositioning U.S. missile defense equipment and sending nuclear-capable stealth bombers on conspicuous missions over South Korea.

At the same time, Kerry attempted to tamp down the significance of a recent U.S. intelligence report that concluded that North Korea is now capable of making a nuclear warhead that can be mounted on a ballistic missile and fired.

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If true, it would mean that North Korea has crossed what many regard as the most difficult technical barrier to being able to launch a nuclear attack, even if limited in scope and range.

Kerry said that “it is inaccurate to suggest” that Pyongyang “has fully tested, developed or demonstrated capabilities that are articulated in that report.”

Kerry was referring to an assessment secretly circulated last month by the Defense Intelligence Agency, a spy service that gathers intelligence and produces analysis for the Pentagon. The finding was made public Thursday when it was mentioned by a Republican congressman during a hearing on Capitol Hill.

North Korea has previously tested stationary nuclear devices, as well as missiles with ranges that could reach parts of the United States. But it has not shown that it has mastered the technical challenge of making a nuclear warhead small and strong enough to be carried by missile to a distant target before detonating.

But Kerry’s use of the phrase “fully tested, developed or demonstrated” seemed to allow for some ambiguity on the question of whether North Korea is capable of making a nuclear warhead, even if it hasn’t exhibited that technology to the outside world.

Statements from the White House and the nation’s intelligence chief included similarly hedged terms.

What may seem like administration obfuscation is “a genuine issue,” said George Perkovich of the Carnegie Endowment for International Peace. “As any of these guys will acknowledge, our intelligence on North Korea is very, very limited. We don’t know what we don’t know.

“A normal country in normal circumstances would not go down the road of relying on such a capability if they haven’t tested it numerous times,” Perkovich said. “When they say they haven’t demonstrated it, that’s true and meaningful . . . but they could have stuff that in desperation they could use. And it could work.”

U.S. officials with access to classified reports said that the DIA tends to go further than other U.S. spy agencies in its assessments of threats, including North Korea’s nuclear program, because of the spy agency’s unique mission.

The DIA is focused on missions that include identifying threats to U.S. forces overseas and making sure that Pentagon leaders are prepared for developments that require a U.S. military response.

Still, officials said that the DIA’s conclusion on North Korea, which it conveyed with “moderate confidence,” is not contradicted by findings from the CIA or other U.S. spy agencies.

“There are some differences [among agencies], but I don’t think they’re huge,” said a Republican member of Congress who spoke on the condition of anonymity, citing the sensitivity of the subject. “There is a growing body of analytic product” on North Korea and its efforts to develop a warhead that suggest “that if they’re not there, they’re close.”

U.S. officials noted that the latest DIA language is consistent with earlier statements from the agency. In 2011, then-DIA Director Ronald Burgess testified that North Korea “may now have several plutonium-based nuclear warheads that it can deliver by ballistic missiles.”

The urgency of that question has been heightened by the menacing behavior of North Korea’s young and relatively untested leader. Last month, the North Korean news agency released pictures of Kim in a “war room” where a large map was marked with lines meant to depict missile flight paths to major cities in the United States.

U.S. officials have said that and other provocative moves seem aimed at bolstering Kim’s standing in North Korea and abroad.

The existence of the DIA’s latest report surfaced at a congressional hearing this week during questioning by Rep. Doug Lamborn (R-Colo.), who read an unclassified portion of what others described as a classified but routine update for policymakers on North Korea’s nuclear program.

South Korean Defense Ministry spokesman Kim Min-seok also sought to play down the significance of the new report in remarks he made during an appearance with Kerry. “Our military’s assessment is that North Korea has not yet miniaturized” a nuclear device, Kim said.

Kerry held crisis talks with officials in Seoul on Friday and heads to Beijing on Saturday to lobby for stronger efforts by China to rein in its reclusive ally. On Sunday, the chief U.S. diplomat is to visit Japan, which, like South Korea, is guaranteed U.S. military protection should North Korea launch an Asian war.

U.S. and Asian diplomats say they doubt North Korea will go that far but acknowledge that a launch of midrange missiles seems increasingly likely, as a show of force meant for U.S. consumption.

Karen DeYoung contributed to this report.