Media playback is unsupported on your device Media caption President Obama: "Together, we have to speak up for the future we seek"

US President Barack Obama has told the Iranian people that a deal to transform the relationship between the two countries could be within reach.

"We have the best opportunity in decades to pursue a different future between our countries," he said in a video message for Persian New Year.

Six world powers are negotiating a deal aimed at limiting Iran's nuclear activity, with a March deadline near.

The president conceded there were still "gaps" in negotiations but was hopeful.

Iran's Foreign Minister Mohammad Javad Zarif said in an apparent response to Mr Obama's video it was time for the US and other negotiating countries - China, France, Germany, Russia and UK - to move forward with an agreement.

"Iranians have already made their choice: Engage with dignity. It's high time for the US and its allies to choose: pressure or agreement," Mr Zarif wrote in a message posted on his official Twitter account.

On Friday, US Secretary of State John Kerry and Mr Zarif met for the fifth consecutive day of talks in Switzerland.

Image copyright AP Image caption An Iranian worker at a Tehran oil refinery

Image copyright AP Image caption John Kerry has represented the US in the nuclear talks

If Iran's leaders agreed to a reasonable deal, then the country would be on a path to prosperity, Mr Obama said.

"I believe that our nations have an historic opportunity to resolve this issue peacefully - an opportunity we should not miss," Mr Obama said in his message celebrating Nowruz.

Isolation awaited if agreement was not reached, he added.

But the president has yet to convince the US Congress of the merits of a deal, and many lawmakers remain opposed to the easing of sanctions.

Earlier this month, 47 Republican senators warned Iran's leaders that any deal on Tehran's nuclear programme could be revoked once Mr Obama leaves office.

The move was condemned by the White House as an attempt to undermine the president's foreign policy.

According to unnamed officials talking to Associated Press news agency, the deal being hatched in the long-running talks will commit Tehran to a 40% cut in the number of machines it could use to make an atomic bomb.

In return, economic sanctions would be eased sharply and a UN embargo on conventional arms would be partially lifted.

Image copyright AFP Image caption Iran's Zarif (left) deep in talks in Lausanne

The sticking points are thought to include the pace at which sanctions would be lifted, how long the deal will last and how much Iran's nuclear facilities will be open to inspection.

On Thursday, a cross-party letter signed by 360 members of Congress was sent to the president, reminding him that the lifting of permanent US sanctions against Iran would require new legislation from Congress.

Iran insists its nuclear programme is solely for peaceful purposes but members of the international community fear it has military ambitions.

The six world powers are hoping to reach a framework agreement by 31 March.