Other than a tweet, President Donald Trump hasn’t said how he’ll stop North Korea from threatening America with a nuclear weapon. And as his Pentagon chief visits key allies in Asia, neither Trump nor his Republican allies in Congress seem settled on any plan. The fight against the Islamic State group is the new administration’s top national security priority, but Defense Secretary Jim Mattis chose South Korea and Japan for his first official overseas trip. Departing Wednesday, Mattis will look to reassure the nations on the front line against North Korea. Americans are seeking reassurance, too. Concern has surged on both sides of the Pacific about the North’s weapons programmes, after leader Kim Jong Un warned in his annual New Year’s address that the country is in the final stages of readiness to test-launch an intercontinental ballistic missile that could potentially threaten the continental United States. In Washington this week, the Senate Foreign Relations Committee held its first policy hearing since Trump took office to discuss North Korea. There were more questions than answers. Last month, Trump fueled speculation of possible US military action to pre-empt North Korea’s weapons development. He tweeted: “Does that mean we have drawn a red line?” Sen. Ben Cardin, Democrat-Maryland, asked at Tuesday’s Senate hearing. Those questions and more will be posed to Mattis when he meets top officials in Seoul on Thursday and Tokyo later in the week, two jittery allies that host nearly 80,000 US troops. During the campaign, Trump complained that defence treaties disadvantaged the US and that he would not rule out abandoning signatories if they refuse to pay more for their defence.