(Adds requests for comment, paragraph 8, detail from statement, paragraph 9, background on sanctions, 10-11)

By Kylie Madry

MEXICO CITY, July 18 (Reuters) - Precursor chemicals used by Mexican cartels to make the deadly opioid fentanyl do not come from China, its embassy in Mexico said on Tuesday, rejecting U.S. officials' accusations.

The embassy said in a statement that China had measures in place to prevent the trafficking of substances used to make illegal drugs, and added the U.S. was "blindly shirking its responsibilities" by not taking domestic action.

"The root of the fentanyl crisis in the United States is within itself," the embassy said.

U.S. President Joe Biden's administration has been seeking cooperation with both Mexico and China in stemming the flow of fentanyl, which has fueled a health crisis and a sharp rise in overdose deaths, as well as its precursor chemicals.

The U.S. Drug Enforcement Administration says the addictive painkiller and its precursors are transported from China to Mexico, the U.S. and Canada, often by international mail.

China had denied the illegal trafficking of fentanyl to Mexico in an April statement, though it did not address precursor chemicals.

The embassy on Tuesday said China was "actively coordinating and strengthening" supervision of drug-making substances with Mexico.

The U.S. embassy in Mexico and Mexico's foreign ministry did not immediately respond to requests for comment.

The Chinese statement, the embassy said, comes after recent comments from U.S. Ambassador to Mexico Ken Salazar and other U.S. officials.

Last week, the U.S. Treasury sanctioned 10 people with suspected ties to the Sinaloa Cartel's fentanyl network, as well as a company accused of importing chemicals from China.

"This represents a blow to (the cartel's) financial operations and illicit activities, since the company receives chemical shipments from China," Salazar said in a statement. (Reporting by Kylie Madry; Editing by Isabel Woodford, Robert Birsel)