WASHINGTON — U.S. Sen. Pat Toomey, R-Pa., joined a Democratic colleague in introducing a measure to hold countries more responsible for fentanyl being trafficked from their borders.

Toomey and Sen. Maggie Hassan, D-N.H., introduced a bipartisan amendment to this year’s National Defense Authorization Act that would require the U.S. to publicly identify countries that are major producers or traffickers of illicit fentanyl — something the government already does for heroin, marijuana and cocaine.

Under the measure, illicit fentanyl-exporting countries would risk losing certain American taxpayer-funded foreign aid unless they schedule fentanyl and its analogues as a class and take steps to prosecute drug traffickers within their borders.

“Illicit fentanyl is seeping into the United States and killing tens of thousands of Americans every year,” Toomey said in a press release. “Countries, like China, that are the primary sources of illicit fentanyl must take action or face consequences for their tacit role in the distribution of this deadly synthetic opioid.

Toomey said the amendment to the NDAA would pressure countries into taking “commonsense measures” to stop the flow of illegal fentanyl from their borders.

Hassan said when she visited China she pushed officials to take aggressive action to crack down on fentanyl trafficking.

She said trafficking out of China has helped fuel the substance-misuse crisis in New Hampshire and across the country, citing the danger of fentanyl in driving addictions and deaths.