President Donald Trump has announced a new order to help the US target people, companies and banks financing and facilitating trade with North Korea.
He also praised China for reportedly ordering banks to stop doing business with Pyongyang.
Mr Trump's actions follow his speech at the UN general assembly this week, when he escalated his rhetoric against North Korea amid a months-long crisis over Kim Jong Un's expanded missile testing programme.
He spoke of his own nation's "patience", but said that if "forced to defend itself or its allies, we will have no choice but to totally destroy North Korea".
Mr Trump said his new executive order would also disrupt other trade avenues for North Korea in efforts to halt its nuclear weapons programme.
He made the announcement on Thursday during a working lunch with Japanese Prime Minister Shinzo Abe and South Korean President Moon Jae-in.
Mr Trump said "tolerance for this disgraceful practice must end now".
He also saluted China's central bank for what he said was a move to stop its banks from trading with North Korea. That development was reported by Reuters on Thursday.
China is North Korea's main trading partner and conduit for international transactions, and Washington has been pushing Beijing to scale back economic and financial ties to further isolate Pyongyang.
Mr Trump, in his address to the UN on Tuesday, said it was "far past time" for the world to confront Kim, declaring that the North Korean leader's pursuit of nuclear weapons poses a threat to "the entire world with an unthinkable loss of human life".
The president said: " Rocket Man is on a suicide mission for himself and his regime," mocking Kim even as he sketched out potentially cataclysmic consequences.
Asked for clarification on Thursday on what circumstances might qualify for the "totally destroy" threat, Mr Trump's national security adviser, HR McMaster, told NBC that would be if North Korea attacked the US or its allies.
Vice President Mike Pence told Fox News Channel on Thursday: "We do not desire a military conflict.
"But the president has made it very clear, as he did at the UN this week, that all options are on the table and we are simply not going to tolerate a rogue regime in Pyongyang obtaining usable nuclear weapons that could be mounted on a ballistic missile and threaten the people of the United States or our allies."
Speaking at the UN on Thursday, Mr Moon took a less confrontational stance than Mr Trump and Mr Abe in their addresses to the world body.
Mr Moon urged North Korea to abandon its nuclear weapons and seek dialogue, and said the stand-off needed to be "managed stably".
Still, when he sat down later with Mr Trump, he complimented the president's "very strong" UN address, saying it would "help to change North Korea".
Mr Trump's overheated language was rare for a US president at the rostrum of the United Nations, but the speech was textbook Trump, dividing the globe into friends and foes and taking unflinching aim at America's enemies.
It drew a sharp rebuke from the North's foreign minister Ri Yong Ho, who said: "It would be a dog's dream if he intended to scare us with the sound of a dog barking."
Despite Mr Trump's rhetoric, his administration insists it is seeking a diplomatic resolution.
Any military intervention designed to eliminate the North's nuclear and missile arsenal would almost surely entail dire risks for US allies in the region, particularly South Korea, lying in range of the North's vast stockpiles of weaponry.
Fears of a military confrontation are increasing.
North Korea conducted a series of provocative launches in recent months, including a pair of intercontinental missiles believed capable of striking the continental United States and another pair that soared over Japanese territory.
It also exploded its most powerful nuclear bomb to date. Prodded by Washington, the UN has responded with the toughest economic sanctions on North Korea yet.
Still, the impasse is no closer to being resolved. Russia and China, which backed the new sanctions, want the US to seek dialogue with the North. American officials say the time is not right for any formal diplomatic process.
But other than using economic pressure to try to compel Pyongyang to give away its nuclear weapons - a strategy that has failed for the past decade - Mr Trump's administration has yet to lay out a strategy for a possible negotiated settlement.
In recent weeks, the administration's lack of direction has been all too apparent, as Mr Trump and other senior officials have vacillated between bellicose talk of possible military action and, at one point, even praise for Kim for a brief lull in missile tests.