The bidding round for exploration and production licences comes as it seeks to revive the sector, hard-hit by international sanctions that were lifted last year.
National Iranian Oil Company head Ali Kardor said the deadline for bids had been pushed back to February 15, ISNA news agency reported.
He said the original late January deadline had been extended because "information from some companies was not complete".
He said British Petroleum had still not submitted a bid.
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"BP has not sent its information to us.
"Although we said this is an official process and you need to enter your information, they haven't done it," he added.
The new licensing round comes a year since a deal between Iran and world powers came into force, lifting international sanctions against Tehran in return for limits on its nuclear programme.
Iran is keen to access new technology to boost its production from fields it shares with its Gulf neighbours.
In early January, it published a list of 29 companies it would allow to bid.
Asian giants including China's CNPC and Sinopec International, the Japanese Mitsubishi Corporation and Japan Petroleum Exploration also put in bids along with companies from Malaysia and South Korea.
Oil-rich Iran has increased production to 3.9 million barrels per day from 2.6 million bpd before President Hassan Rouhani took office in 2013.
It has also earned more than USD 2 billion (1.9 billion euros) from gas sales since sanctions were lifted, Kardor said.
The country has already signed a flurry of deals with international companies.
In December, Tehran signed a memorandum of understanding with Russia's Gazprom on the development of two major oilfields.
Also in December, it signed three preliminary deals with Shell to examine developing major oil and gas fields.