Washington, DC - US President Donald Trump will seek to raise international economic and political pressure on North Korea as he visits Japan, South Korea, and China, amid nuclear tensions and rising calls for serious negotiations that the president so far has rejected.

Legislators and foreign policy analysts in the United States are watching closely to see whether Trump, on a 12-day trip to the Asia-Pacific region, continues his threatening rhetoric at Pyongyang or pivots towards diplomacy, as Secretary of State Rex Tillerson and Secretary of Defense James Mattis have advocated.

"We need to support our diplomatic team in every way that we can, because short of us, collectively with China and few other countries being able to change the dynamic, we are heading to a very bad place," Senator Bob Corker, Republican chairman of the Senate Foreign Relations Committee, told Al Jazeera.

Trump has escalated US military deployments in Northeast Asia, sending F-35s, the US' most advanced fighter jets, to Japan. He also followed through with the deployment of a THAAD anti-missile system in South Korea, over China's objections, and sent three aircraft carrier strike groups to the Pacific.

'Minimalist talks'

In tweets, the president has belittled North Korea's ruler Kim Jong-un as "rocket man" and said Tillerson was "wasting his time" trying to engage in talks. Behind the scenes, the president is said to have effectively shut down US diplomatic efforts to talk to the North Koreans through the United Nations, the so-called New York channel, worrying US legislators.

"The minimalist talks that existed are breaking down. He's made it pretty clear he has no interest in keeping open a dialogue with North Korea," Senator Chris Murphy, a Connecticut Democrat and Trump critic, told Al Jazeera.

"No one has been authorised to negotiate by this administration. They need to start over with a strategy that gradually builds up political, economic, and military pressure - ultimately leading to negotiations they have been unable thus far to put together."

Pyongyang has responded to Trump with threats to test a powerful hydrogen bomb over the Pacific Ocean, and issued statements suggesting the president needs medication, calling Trump an "aged retard", famously translated in the US from Korean to English as "dotard".

The back and forth has raised alarm worldwide and underlined both Kim and Trump's unpredictability - and relative inexperience on the world stage.

South Korea President Moon Jae-in, who has sought detente with the north, has called on the US not to take any military action without South Korea's agreement. Trump has personally disparaged Moon and opened up the question of the Korea-US Free Trade Agreement, which has strategic implications.

"The president wants to be in a position that the message that Kim Jong-un receives is that there is a solid front, with no cracks in the mutual security agreement of Korea with the United States," said Don Manzullo, president of the Korea Economic Institute of the US, which supports US-Korea trade.

"Un has to realise that the world is united against him."

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Trump will travel first to Japan on Sunday where he will meet with newly re-elected Prime Minister Shinzo Abe, who has taken a hawkish line on North Korea, advocating at the UN for tougher sanctions and at home for a more robust Japanese military posture. Trump and Abe will hold a bilateral summit and a press conference.

"Abe seems to be a bit more of a hawk than South Korea. But ultimately, if the United States supports diplomacy, then everybody in the region supports it too because nobody wants a war," said Tom Z. Collina, director of policy for the Ploughshares Fund, a non-profit group that advocates the elimination of nuclear weapons.

"This trip is an opportunity for Trump himself to pivot towards diplomacy as the main way to solve the North Korea crisis, but he may not take it," Collina told Al Jazeera.

In advance of the president's trip, the White House announced moves designed to increase pressure on both North Korea and China.

Chinese solution?

Officials said Trump will use his meeting with China President Xi Jinping to take tougher measures against North Korea. The Treasury Department announced on Thursday it was cutting off the small Chinese Bank of Dandong from an international transaction network, alleging the bank had helped finance North Korea's missiles.

"China is part of the solution to any coherent North Korea strategy, but the strategy needs to start with alliances, and the most concerning thing is the state of the US-South Korea alliance," said Brian Harding, director for Asia-Pacific security policy at the Center for American Progress and a former Defense Department adviser in the Obama administration.

Back home in Washington, the US Congress is advancing additional financial sanctions while signaling legislators are prepared to rein in Trump's ability to launch a military attack. The key objective, they say, is getting North Korea to negotiate.

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"It's important that we reassure our allies, South Korea and Japan, that we stand with them, that we are solid," Senator Chris Van Hollen, a Maryland Democrat and sponsor of a new bank sanctions bill, told Al Jazeera. "We will not accept a North Korea with nuclear weapons and we need to keep pushing. We have got to exert more pressure on North Korea."

But sanctions and military pressure are unlikely to yield results without presidential leadership from Trump on negotiations, experts say.

"You don't know what the North Koreans are up to unless you negotiate and talks are not the same thing as negotiations," said Leon V Sigal, director of the Northeast Asia Cooperative Security Project at the Social Science Resource Council in New York and author of the 1998 book, Disarming Strangers: Nuclear Diplomacy with North Korea.

"The US needs to put a proposal on the table to address their security needs in return for a suspension of the nuclear programmes. That's the best you can do right now," Sigal said.