WASHINGTON, June 5 (Reuters) - U.S. President ‌Donald Trump's special envoy Steve Witkoff and son-in-law ​Jared Kushner traveled to the Oak Ridge National Laboratory in Tennessee on Thursday to consult with experts that could play a role in nuclear negotiations with Iran, a source familiar with the trip said on Friday.

The source, confirming an Axios report, did not provide additional details.

President Donald Trump is adamant that any deal to end the war with Iran include a provision that Tehran will not develop a nuclear weapon.

Iran is believed to possess about 900 pounds of highly enriched uranium that was at sites bombed by U.S. planes a year ago. Tehran has been adamant that it must maintain the ability to enrich uranium and denies developing a weapon.

(Reporting by Steve Holland and Christian Martinez; Editing by Ryan Patrick Jones and Cynthia Osterman)