BEIJING, SEPT. 11 -- An Iranian diplomat acknowledged today that Iran has Chinese-made missiles but claimed that they were captured from Iraq rather than purchased from China.

Deputy Foreign Minister Ali Mohammed Besharati said that he had arrived in China for consultations at a "critical juncture," just before a visit to Iran by U.N. Secretary General Javier Perez de Cuellar.

The United States has accused China of selling weapons to Iran, including Silkworm antiship missiles. China has repeatedly denied selling such weapons to Iran and has proclaimed its neutrality in the nearly seven-year-old Iran-Iraq conflict.

In a press conference, Besharati said, "We have Chinese-made missiles available and at our disposal but we have not received them from China. We captured them from the Iraqis . . . . "

Besharati's was the most explicit statement made here to date that Iran does possess Silkworm missiles.

Besharati said, meanwhile, that it was "just a coincidence" that he happened to be in Beijing at the same time as Iraq's parliamentary speaker, Saadun Hammadi. Both men arrived here yesterday.

The Iraqi official is believed to be pressing the Chinese to support a United Nations arms embargo against Iran if the Tehran government refuses to accept a cease-fire resolution adopted by the U.N. Security Council in July. China is one of five permanent members of the Security Council.

Besharati said that China had encouraged Iran to receive Perez de Cuellar, who is attempting to mediate a cease-fire based on the Security Council resolution. Iraq has said it would accept the resolution if Iran does. Iran has criticized the resolution but has not formally rejected it.