BEDMINSTER, New Jersey >> President Donald Trump today issued another warning of swift and forceful retaliation against nuclear North Korea, declaring the U.S. military “locked and loaded.” He said the isolated nation’s leader “will regret it fast” if he takes any action against U.S. territories and allies.

The latest threat appeared to draw another red line that would trigger a U.S. attack and for a fourth day in a row ratcheted up a rhetorical standoff between the two nations. Trump’s comments, however, did not appear to be backed by significant military mobilization on either side of the Pacific, and an important, quiet diplomatic channel remained open.

Speaking to reporters from his New Jersey golf resort, Trump declined to explain precisely what he meant by the boast of military readiness. He brushed away calls for caution from world leaders, including Germany’s Angela Merkel. And he directly called out Kim Jong Un, North Korea’s leader, as a destabilizing force who should not be allowed to continue his course.

“If he utters one threat in the form of an overt threat — which by the way he has been uttering for years and his family has been uttering for years — or he does anything with respect to Guam or anyplace else that’s an American territory or an American ally, he will truly regret it and he will regret it fast,” Trump said.

The compounding threats came in a week in which the longstanding tensions between the U.S. and the communist country seemed to abruptly boil over. New United Nations sanctions condemning the North’s rapidly developing nuclear program drew fresh ire and threats from Pyongyang. Trump responded by vowing to rain down “fire and fury” if challenged. The North then threatened to target Guam, a tiny U.S. territory some 2,000 miles from Pyongyang.

Trump offered reassurance to Guam. “I feel that they will be very safe, believe me,” Trump told reporters today, with Secretary of State Rex Tillerson and U.N. Ambassador Nikki Haley at his side.

#USAF B-1B Lancer #bombers on Guam stand ready to fulfill USFK’s #FightTonight mission if called upon to do so https://t.co/O3oVeFrNrG pic.twitter.com/IAm2qLwcWY

— U.S. Pacific Command (@PacificCommand) August 11, 2017

Tough talk aside, The Associated Press reported today that talks between senior U.S. and North Korean diplomats continue through a back channel previously used to negotiate the return of Americans held in North Korea. The talks have expanded to address the deterioration of the relationship, according to U.S. officials and others briefed on the process. They weren’t authorized to discuss the confidential exchanges and spoke on condition of anonymity.

Still, Trump today sought to project military strength. He also spoke of pursuing more sanctions on North Korea.

He tweeted: “Military solutions are now fully in place, locked and loaded, should North Korea act unwisely. Hopefully Kim Jong Un will find another path!”

Trump later retweeted a posting from U.S. Pacific Command that showed B-1B Lancer bomber planes on Guam that “stand ready to fulfill USFK’s #FightTonight mission if called upon to do so.”

Such declarations, however, are not necessarily indicators of a new, more aggressive posture. “Fight tonight” has long been the motto of U.S. forces in South Korea to show they are always ready for combat on the Korean Peninsula.

U.S. officials insist there have been no new significant movement of troops, ships, aircraft or other assets to the region other than what has already been long planned for previously scheduled exercises.

American and South Korean officials said they would move forward later this month with the exercises, which North Korea claims are a rehearsal for war.

All the war talk in recent days has alarmed international leaders.

Russia’s foreign minister, Sergey Lavrov, estimated the risk of a military conflict between the U.S. and North Korea as “very high,” and said Moscow was deeply concerned.

“When you get close to the point of a fight, the one who is stronger and wiser should be the first to step back from the brink,” Lavrov said today.

“I don’t see a military solution and I don’t think it’s called for,” said German Chancellor Angela Merkel. She declined to say whether Germany would stand with the U.S. in case of a military conflict with North Korea and called on the U.N. Security Council to continue to address the issue.

“I think escalating the rhetoric is the wrong answer,” Merkel added.

“Let her speak for Germany,” Trump said, when asked about the comment. “Perhaps she is referring to Germany. She’s certainly not referring to the United States, that I can tell you.”

Trump’s rhetoric stands in contrast to an ongoing back channel for negotiations between the United States and North Korea. People familiar with the contacts say the interactions have done nothing thus far to quell tensions over North Korea’s nuclear weapons and missile advances. But they say the behind-the-scenes discussions could still be a foundation for more serious negotiation.

Despite the tensions, life on the streets of the North Korean capital remains calm. There are no air raid drills or cars in camouflage netting as was the case during previous crises.

North Koreans have lived for decades with the state media message that war is imminent, the U.S. is to blame and their country is ready to defend itself. State-run media ensure the population gets the North Korean side of the story, without any sense of international concern about the situation.

As it is, the U.S. has a robust military presence in the region, including six B-1 bombers in Guam and Air Force fighter jet units in South Korea, plus other assets across the Pacific Ocean and in the skies above. U.S. military options range from nothing to a full-on conventional assault by air, sea and ground forces. Any order by the president could be executed quickly.

The U.S.-South Korea exercises are an annual event, but they come as Pyongyang says it is readying a plan to fire off four Hwasong-12 missiles toward the tiny island, which is a U.S. territory and major military hub. The plan would be sent to Kim for approval just before or as the U.S.-South Korea drills begin.

Called Ulchi-Freedom Guardian, the exercises are expected to run Aug. 21-31 and involve tens of thousands of American and South Korean troops on the ground and in the sea and air. Washington and Seoul say the exercises are defensive in nature and crucial to maintaining a deterrent against North Korean aggression.

Talmadge contributed from Seoul, South Korea. Associated Press writers Josh Lederman, Matthew Pennington and Lolita C. Baldor in Washington contributed to this report.