North Korea abruptly canceled talks with Seoul scheduled for Wednesday and threatened to walk away from the June summit with Washington, blaming the joint U.S. and South Korean military exercises in the region.
The North's state-run news agency described the ongoing military drills as a "provocation" and a test run for a future invasion.
Collins described Pyongyang's reaction to the planned military exercises as a "cover to express their dissatisfaction with a bunch of different issues."
"North Korea does normally take issue with military exercises, but these were announced several weeks ago and even the South Koreans said that Kim Jong Un was willing to overlook the U.S. and South Korean exercises happening in the region," Collins said.
The Pentagon said the U.S. training with the South Koreans is part of an "annual training program to maintain a foundation of military readiness."
"While we will not discuss specifics, the defensive nature of these combined exercises has been clear for many decades and has not changed," Defense Department spokesman U.S. Army Col. Rob Manning said in a statement Tuesday.
North Korea's withdrawal from talks with the United States would deal a major blow to what Trump has already described as his "proudest achievement" — denuclearizing the Korean Peninsula.
Joel Wit, a senior fellow at Columbia University's Weatherhead East Asian Institute and founder of 38 North, said the move from the North could be a way "to heighten tension around the upcoming summit."
"Just as how President Trump said he'd be willing to walk out of the meeting if it wasn't a good deal, I think they are sort of doing the same thing," Wit said. "I think it's part posturing but also a reflection of some serious substantive difficulties and differences that we need to have worked out before the summit. I mean, leaders don't just come to a meeting and negotiate with each other; everything is worked out beforehand."
Wit, who spent six years working on the Clinton-era Agreed Framework and another 15 years at the State Department engaged in arms control and non-proliferation issues, noted North Korea's aversion to national security advisor John Bolton.
Bolton, a former United Nations ambassador, penned an op-ed in The Wall Street Journal titled "The Legal Case for Striking North Korea First" weeks before becoming Trump's third national security advisor.