British Airways, owned by IAG, announced plans to renew links with the Iranian capital in February after sanctions on the country were lifted. It had stopped flights in 2012 due to a combination of commercial and political reasons.

The flights had been due to start from mid-July, but will now start on Sept. 1, with British Airways confirming in its statement that the route remained an important one.

"While preparations for the new route have generally been progressing well, some technical issues have arisen which make it sensible for us to put back the launch of flights," the airline said.

British Airways declined to comment on the nature of the technical issues.

(Reporting by Sarah Young; Editing by Alexandra Hudson)