WASHINGTON — The Trump administration has all but abandoned its early message that the Syrian missile strikes were an isolated military action, not part of a larger plan for dealing with U.S. enemies. On Monday, Vice President Michael Pence signaled to North Korea that, under certain circumstances, it could face similar treatment.

“Just in the past two weeks, the world witnessed the strength and resolve of our new president in actions taken in Syria and Afghanistan,” the vice president said during a visit to South Korea, referring as well to the U.S. dropping the most powerful non-nuclear bomb in its arsenal last week in Afghanistan.

“North Korea would do well not to test his resolve or the strength of the armed forces of the United States in this region,” Pence said. “The era of strategic patience is over.”

But there were no signs that the new approach had prompted the regime of Kim Jong Un to dial back its belligerency and its nuclear weapons program.

On Monday, North Korea’s deputy United Nations ambassador, Kim In Ryong, accused the United States of creating “a dangerous situation in which a thermonuclear war may break out at any moment.”

Analysts questioned whether the United States could duplicate its Syria and Afghanistan strikes against North Korea, which has spent decades hardening its nuclear and missile programs against attack.

“The United States does not have any good military options against North Korea,” said Bonnie Glaser, a specialist in Asian-Pacific security at the Center for Strategic and International Studies. Comments by Pence and others in the administration “seem like posturing to me.”

After U.S. forces fired 59 Tomahawk missiles at Syria on April 7, Pentagon and Trump administration officials initially described the strike as a “one-off” operation aimed solely at preventing further use of chemical weapons by Syrian President Bashar Assad.

More recently, the administration has shifted the message, using the missile strike and last week’s bombing of Islamic State tunnel complex in Afghanistan to send a warning to North Korea and other potential adversaries.

Speaking Sunday on ABC, Trump’s national security adviser, Army Lt. Gen. H.R. McMaster, noted the connection between Syria, Afghanistan and the Korean Peninsula. “This national security team is capable of rapidly responding to those sorts of crises or incidents and events and providing the president with options,” McMaster said.

“There have been mixed signals coming out about both strikes,” in Syria and Afghanistan, said Anthony Ruggiero, a senior fellow and North Korea specialist with the Foundation for Defense of Democracies, a Washington think tank. He called Pence’s remarks Monday the “clearest yet” by the administration about using Syria and Afghanistan as potential deterrences against Pyongyang.

During his campaign last year, Trump pledged to put America first and not engage in military adventures like President George W. Bush’s Iraq War and President Barack Obama’s intervention in Libya. But he was highly critical of North Korea’s Kim and now appears ready to deploy not just harsh rhetoric, but also the U.S. military against Kim’s regime.

Last week, the Pentagon sent the USS Carl Vinson aircraft carrier and other warships for maneuvers off North Korea.

North Korea showed off some of its latest weapons technology in a parade honoring Kim’s late grandfather Saturday. In addition, analysis of satellite imagery suggests North Korea is preparing to conduct a new underground detonation at Mount Mantap, a peak in the northeast of the country where the regime tests its warheads.

On Sunday, North Korea fired another missile — presumably another test — but it failed soon after launch.

White House press secretary Sean Spicer Monday praised Chinese leaders for playing “a more active role” in pressuring North Korea. “We’re going to continue to urge China to exhibit its influence in the region to get better results,” he said.

As Spicer noted, Beijing announced in February that it was halting coal imports from North Korea, depriving Pyongyang of a source of currency. Overall, China has been an uneven collaborator with the United States in confronting North Korea. According to Chinese data, trade with North Korea grew 37 percent in the first quarter, from the comparable quarter last year.

China has made it clear that it doesn’t want to destabilize North Korea to the degree that the regime collapses and chaos ensues. For that reason, it has worked through the United Nations to limit sanctions on its rogue neighbor, including calls to cut off crude oil shipments to North Korea. China is the main source of those shipments.