President Trump has little chance of persuading China and Russia to cut off North Korea's oil supply, and even if he succeeds the unprecedented step may still not be enough to get Kim Jong Un to stop building nuclear weapons.
The U.S. wants the U.N. Security Council to approve a range of new sanctions, including a full ban on exports of oil to North Korea, after Pyongyang carried out its biggest ever nuclear bomb test on Sunday.
Experts say an oil embargo would be a major shift in international efforts to squeeze Kim's regime.
"Something like this has not been tried before," said Kent Boydston, a research analyst at the Peterson Institute for International Economics. "It would be a different kind of sanction that would have broader impact on the economy."
A prolonged halt in oil supplies could eventually bring the North Korean economy to its knees. But it would need the support of China, North Korea's main trading partner, and Russia -- both of which can veto the measure at the U.N.
Related: U.S. proposes U.N. resolution to ban oil exports to North Korea
"Given the new developments on the Korean Peninsula, China agrees that the [Security Council] should make further responses and take necessary measures. China will make close communication with relevant parties with an objective, fair and responsible attitude," Chinese Foreign Minister Wang Yi said Thursday.
But the escalating crisis over North Korea is a thorny problem for President Xi Jinping, who is trying to project strength and stability ahead of a key meeting of the Chinese Communist Party next month.
That makes experts skeptical that he will take drastic measures at this point against Kim.
Beijing doesn't want to confront Pyongyang
"It is already crystal clear that China will not curtail [North Korea's] energy supply," wrote Peter Hayes and David von Hippel of the Nautilus Institute, a think tank that specializes in energy issues, in a report this week.
Global Times, a Chinese state-run tabloid that often expresses nationalistic views, suggested in April that Beijing might cut off North Korea's oil supply if it carried out another nuclear test.
After Pyongyang went ahead with the test this week, the newspaper poured cold water on the idea of an oil ban, warning it wouldn't necessarily rein in Kim's nuclear program and could spark a confrontation with North Korea.
Related: What's left to sanction in North Korea after its big nuclear test?
Halting or reducing energy supplies now would "reduce whatever influence the Chinese have left in Pyongyang," the Nautilus experts said.
Experts say China is the key supplier, sending crude oil to its smaller neighbor through a pipeline. But it stopped publishing data about how much oil flows across the border over three years ago.
So even if Beijing agreed to limit oil exports, it would be tricky to monitor.
People would suffer most, not the military
Russian President Vladimir Putin is also opposed to an oil embargo, telling South Korean President Moon Jae-in on Wednesday that he's concerned it may harm civilians, according to a spokesman for Moon.
Hayes and von Hippel say that it would be unlikely to have much of an effect on North Korea's military and nuclear programs in the short term because they can draw on stockpiles.
The bigger impact would be felt by the wider population.
"People will be forced to walk or not move at all, and to push buses instead of riding in them," Hayes and von Hippel wrote. "There will be less light in households due to less kerosene."
They predict North Koreans would turn to other energy sources like coal and solar panels for cooking and power.
-- Serenitie Wang in Beijing contributed to this article.
