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WASHINGTON) — Having lost patience with China, the Trump administration is studying new steps to starve North Korea of cash for its nuclear program, including an option that would infuriate Beijing: sanctions on Chinese companies that help keep the North’s economy afloat.

It’s an approach that’s paid off for the U.S. in the past, especially with Iran, where American economic penalties helped drive Tehran to the nuclear negotiating table. Yet there are significant risks, too, including the possibility of opening a new rift with Beijing that could complicate U.S. diplomatic efforts on other critical issues.

The renewed look at “secondary sanctions” comes as Washington seeks a forceful response to North Korea’s test this week of an intercontinental ballistic missile that could strike the United States. Few are advocating a military intervention that could endanger millions of lives in allied South Korea across the border. But options for turning the screw on the North financially also are imperfect.

Already, a wide array of U.S. and international sanctions target North Korean entities and officials, making it illegal for Americans to do business with them. The U.S. also has pursued companies outside North Korea accused of surreptitiously helping the communist country, such as a small Chinese bank the U.S. penalized last week for allegedly laundering money for North Korea.

But the U.S. thus far has avoided what sanctions experts describe as a logical escalation: secondary sanctions targeting banks and companies that do any business with North Korea — even legitimate transactions that aren’t explicitly prohibited by U.N. Security Council resolutions.

The world must do more to “cut off the major sources of hard currency to the North Korean regime,” Nikki Haley, President Donald Trump’s U.N. ambassador, said at an emergency session of the council Wednesday.