WASHINGTON (Reuters) - Frustrated U.S. lawmakers called on Tuesday for a high-powered response to North Korea’s nuclear tests, saying Washington should act alone if necessary to stiffen sanctions on companies from China, Russia and any country doing business with Pyongyang.

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“I believe the response from the United States and our allies should be supercharged,” said Representative Ed Royce, chairman of the House of Representatives Foreign Affairs Committee.

“We need to use every ounce of leverage ... to put maximum pressure on this rogue regime,” the Republican congressman told a hearing on North Korea. “Time is running out.”

The U.N. Security Council stepped up sanctions on Monday following Pyongyang’s sixth nuclear test on Sept. 3, imposing a ban on textile exports and capping oil imports.

It was the ninth sanctions resolution unanimously adopted by the council since 2006 over North Korea’s ballistic missile and nuclear programs. To win Chinese and Russian support, Washington dropped demands including a bid for an oil embargo.

At the hearing, U.S. officials released American intelligence findings on how North Korea smuggles coal and commodities to Russia and China.

Assistant Treasury Secretary Marshall Billingslea displayed slides showing ships he said picked up coal and other commodities in North Korea, illegally turning off their electronic identification systems to hide the fact that they were carrying cargo to China and Russia.

“Pyongyang falsifies the identity of vessels to make it harder for governments to determine if ships docking in their ports are linked to North Korea,” Billingslea said.

An Aug. 5 U.N. resolution banned North Korean exports of coal.

Russia and China both say they respect U.N. sanctions.

Committee members expressed frustration that previous sanctions had not deterred Pyongyang.

“We’ve been played by the Kims for years,” Republican Representative Ted Poe said, referring to North Korean leader Kim Jong Un and his predecessors.

Lawmakers pressed Billingslea, and Acting Assistant Secretary of State Susan Thornton for evidence new sanctions would be more effective.

They acknowledged there had not been sufficient evidence that past sanctions had worked, but insisted the administration would work for a better result this time.

“We can designate Chinese banks and companies unilaterally, giving them a choice between doing business with North Korea or the United States,” said Royce, who had breakfast on Tuesday with Secretary of State Rex Tillerson.

“We should go after banks and companies in other countries that do business with North Korea the same way,” he said.