Any nuclear deal with Iran and multinational powers will pave the way for more oil exports and therefore influence world markets, a lawmaker in Tehran said.

Ali Marvi, the head of an energy committee inside the Iranian parliament, said Iran would be influential on the world oil stage if an agreement is reached.

"Black gold prices are currently growing in the world markets and sanctions relief on Iran will pave the way for more exports," he said Monday. "Therefore, this [nuclear] issue will affect world [oil] prices."

Members of the Republican-led Congress in the United States said they would be reluctant to lift sanctions on Iran without any verifiable assurances the path to a nuclear weapon would be blocked for the Islamic Republic.

U.S. Secretary of State John Kerry returns this week to Lusanne, Switzerland, to take part in the multilateral talks on Iran's nuclear program, which the country maintains is for peaceful purposes. State Department spokeswoman Marie Harf said during a Monday press briefing there was unity inside the negotiating room.

"I understand there's lots of talk publicly about this issue," she said. "What we're focused on is what actually happens in the negotiating room and seeing if we can get to an agreement."

On the stance taken by Republican leaders, Mehdi Hosseni, the head of the contracts division at the Iranian Oil Minister, said last week U.S. oil companies would be rewarded if they took a stance against their position.

Iranian crude oil exports are restricted to around 1 million barrels per day and only to six nations under the terms of a joint action plan enacted in November 2013.

Marvi said he expected oil prices for the year would level out at around $85 per barrel, about $20 above other estimates.