A group of U.S. senators visiting China to discuss trade and security have questioned Beijing about reports that missiles it sold to Iran ended up in the hands of the militant group Hezbollah in Lebanon. The senators also urged China to push North Korea to return to negotiations on ending its nuclear weapons program.

The eight U.S. senators said Friday that when Chinese officials were asked about missiles sold to Iran they would only confirm a sale to what they called a "sovereign country."

Senator Arlen Specter of Pennsylvania

Senator Arlen Specter of Pennsylvania, says officials in Beijing told his group the missile sale had been made under Chinese regulations forbidding resale or transfer to a third party.

"Then the questions arose that in light of the transfer in violation of the arrangement between China and Iran would China continue to sell missiles to Iran," said Mr. Specter.  "And there was no response on that."

The militant group Hezbollah reportedly fired a Chinese-made missile at an Israeli warship in July, sparking concerns that missiles China had sold to Iran were ending up with Hezbollah.

The U.S. has previously imposed sanctions on several Chinese companies for transferring restricted equipment and technology to Iran that could be used in weapons of mass destruction. 

However, the senators did praise China for supporting a U.N. Security Council resolution condemning North Korea's July missile launches.

Senator Specter said he urged China to use its long-standing relationship with North Korea to encourage the isolated nation back to negotiations on its nuclear weapons programs.

China has previously hosted six-party talks on Pyongyang's nuclear weapons program, which also include South Korea, Japan, Russia and the United States.

Negotiations have stalled since September, after Washington imposed financial sanctions on North Korea, alleging Pyongyang was involved in counterfeiting and drug smuggling. 

On trade, the senators said Friday the U.S. economic relationship with China was good overall, but intellectual property rights protection was poor and market access too restricted.

Senator Lamar Alexander of Tennessee

Senator Lamar Alexander of Tennessee said the auto parts market in China was one area U.S. manufacturers considered too restrictive.

"If China is going to have such important access to the U.S. market with such a variety of goods, the American automobile companies and particularly the automobile suppliers need to have a clear opportunity to be here and to compete here and to make money here," said Senator Alexander.

The senators' six-day trip to China was the third dialogue between legislators of the two countries.  The U.S. lawmakers were due to meet with Chinese President Hu Jintao on Saturday.