The Trump administration is preparing new sanctions on North Korea, a day after declaring it a state sponsor of terrorism in a move to put additional pressure on Pyongyang's nuclear programme.
North Korea has joined Iran, Sudan and Syria on America's terror blacklist, a largely symbolic step as the administration already has the authority to impose virtually any sanctions it wants on Kim Jong Un's government over its nuclear weapons development.
As part of its "maximum pressure" campaign, President Donald Trump said the Treasury Department would impose more sanctions on North Korea and "related persons" starting today, without hinting who or what would be targeted.
The move is part of a rolling effort to deprive Pyongyang of funds for its nuclear and missile programmes and leave it internationally isolated.
"It will be the highest level of sanctions by the time it's finished over a two-week period," Mr Trump said.
Secretary of State Rex Tillerson said on Monday the pressure campaign was starting to bite in Pyongyang, which is already facing unprecedented UN-mandated sanctions over its nuclear and ballistic missile tests.
Mr Tillerson said anecdotal evidence and intelligence suggests the North is now suffering fuel shortages, with queues at petrol stations, and its revenues are down.
The US has been applying sanctions of its own as well.
In Tokyo, Japan's Prime Minister Shinzo Abe welcomed the move, telling reporters Japan supports the step as a way to increase pressure on North Korea. But Chinese Foreign Ministry spokesman Lu Kang expressed concern.
Mr Lu said that the situation is "highly sensitive" and that it would be "helpful to bring all parties back to the negotiation table instead of doing the opposite".
Da Zhigang, a North Korea expert at the Heilongjiang Academy of Social Sciences, said the move "will arouse diplomatic reactions and hatred toward the US from North Korea" and could even prompt the North to resume missile tests.
An editorial on Tuesday in North Korea's ruling party newspaper, Rodong Sinmun, called Mr Trump a "heinous criminal" who had insulted the dignity of the country's supreme leadership and its socialist system during his recent visit to South Korea.
The editorial, carried by the state-run news agency, threatened "merciless punishment". It did not mention the terror designation.
In September, Mr Trump opened the way for the US to punish foreign companies dealing with North Korea. He issued an executive order expanding the Treasury Department's ability to target anyone conducting significant trade in goods, services or technology with the North, and to ban them from interacting with the US financial system.
Bruce Klingner, senior research fellow on Northeast Asia at the conservative Heritage Foundation, said the Treasury could be preparing more designations against North Korean entities related to the terrorism listing, or possibly Chinese or other companies violating the September order.
A potential target would be Chinese banks that serve as North Korea's conduit to the international system. Such a move would irk Beijing, whose help Mr Trump is counting on to put an economic squeeze on Pyongyang.
Mr Tillerson urged China, which accounts for 90% of North Korea's external trade, to take unilateral steps to cut fuel supplies to its wayward neighbour. China, which is calling for dialogue to ease the nuclear tensions, is reluctant to exert economic pressure that could destabilise the North.
Mr Tillerson acknowledged a two-month pause in the North's rapid tempo of nuclear and missile tests and said there was still hope for diplomacy. With tougher sanctions in the offing, he warned Kim: "This is only going to get worse until you're ready to come and talk."
North Korea has been on and off the terror list over the years. It was designated for two decades because of its involvement in international terror attacks in the 1980s, then taken off in 2008 to smooth the way for nuclear talks that soon failed.