WASHINGTON (Reuters) - President Donald Trump’s cancellation of a summit with North Korean leader Kim Jong Un risks a return to crisis mode between Washington and Pyongyang but both sides may be wary of letting the situation escalate into fears of war as it did last year.

North Korean leader Kim Jong Un inspects the completed railway that connects Koam and Dapchon, in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang May 24, 2018. KCNA/via REUTERS

With a new exchange of super-charged rhetoric driving the United States and North Korea from the negotiating table, there is growing concern that words could be matched with action, including renewed shorter-range missile tests or stepped-up cyber attacks by Pyongyang and increased sanctions or deployment of new military assets by Washington, analysts said.

But with Trump saying he is keeping the door open to diplomacy and North Korea apparently still looking to benefit from a thaw with South Korea, such steps could be constrained - or at least tempered - by a mutual desire to keep things from spiraling out of control.

Even so, Trump, in scrapping the June 12 summit in Singapore, sounded a bellicose note on Thursday, warning Kim of the United States’ greater nuclear might, reminiscent of the president’s tweet last year asserting that he had a “much bigger” nuclear button than Kim.

That followed North Korea’s warning earlier in the day that it was prepared for a nuclear showdown with Washington, a threat that U.S. officials said contributed heavily to Trump’s decision to call off the summit.

“The decision to cancel the planned summit and the manner in which it was done have the potential to put us back on a glide path to conflict,” said Ned Price, a former CIA officer who served as National Security Council chief spokesman in the Obama administration.

Some other analysts took a more cautious view.

“It’s too early to bang the war drums,” said Bruce Klingner, an Asia expert at the conservative Heritage Foundation think tank. “We may get there, but I think it’s premature to jump to that conclusion now.”

North Korea’s pursuit of nuclear weapons raised fears of war last year amid an exchange of insults and threats between Trump and Kim over Pyongyang’s testing of an H-bomb and its work on a missile capable of hitting the United States. But tensions eased in recent months, only to reignite in the past week.

HOW WILL NORTH KOREA RESPOND?

Much will depend on what North Korea does next, experts say. Most remain more skeptical than ever about Kim’s willingness to give up his nuclear arsenal and believe Trump was naive to believe that he would.

In Pyongyang’s first response to Trump’s cancellation of the summit, North Korea’s vice foreign minister said the country was still open to resolving issues with the United States “at any time in any way.” But he gave no indication Pyongyang was willing to bargain away its nuclear program.

If Kim decides on a more aggressive response to Trump’s move, he could test one of his short- or mid-range missiles, something North Korea has refrained from doing in recent months while pursuing diplomatic outreach, analysts said.

North Korea could also decide on a riskier course: a resumption of the testing it formally suspended last month on intercontinental ballistic missiles it says are capable of hitting the United States.

Pyongyang’s rapid ICBM advance was what originally put Trump and Kim on a collision course and, according to U.S. officials, led him at one point to ask the Pentagon to draw up options for a preventive strike on a North Korean nuclear or missile site.

“An early indication of a downward turn in the state of affairs would be North Korean statements that they are no longer bound by their testing moratorium,” said Victor Cha, a former Asia adviser under President George W. Bush.

Another possibility is increased North Korean cyber attacks.

“We expect that there will be some type of cyber-retaliation, most likely denial-of-service or other disruptive attacks against U.S. government departments or military networks, defense contractors, and large American multinationals,” said Priscilla Moriuchi, former head of the National Security Agency’s East Asia and Pacific cyber threats office.

But Jeff Bader, who served as former President Barack Obama’s chief Asia adviser, said Kim would likely avoid “excessive provocations” because he hopes to continue improving relations with South Korea, which in itself could drive a wedge between allies Washington and Seoul.

“That would restrain him for a while,” said Bader. “Over the longer term, sure, he’ll go back to provocations, I don’t doubt that.

The Trump administration has signaled it is considering further sanctions against North Korea under its “maximum pressure” campaign. That could also mean increased efforts to intercept ships suspected of violating international sanctions.

China, North Korea’s main trading partner, has the potential to complicate matters if it eases sanctions enforcement that Washington saw as helping to draw North Korea into negotiations.

Other possibilities include beefing up U.S. air and naval assets in and around South Korea and continuing to defy North Korea’s demands for an end to U.S.-South Korean military drills.

But Evans Revere, a former U.S. negotiator with North Korea, said significant U.S. military moves seemed unlikely “unless some North Korean provocation or action requires them to be dusted off again.”