Iran foreign minister Mohammad Javad Zarif and Russian’s FM expressed optimism an initial agreement was within reach.
British Foreign Secretary Philip Hammond sounded a note of caution. "I think we have a broad framework of understanding, but there are still some key issues that have to be worked through," he told the BBC.

Senior Iranian negotiator Abbas Araqchi told Iran television. "We insist on keeping research and development with advanced centrifuges," he said.

Araqchi said he expected the parties to issue a joint statement declaring that "progress has been made in the talks and that we have come to a solution on key issues. We will have the solutions in written form.

Russian Foreign Minister Sergei Lavrov, who returned to Moscow, said negotiators had reached a general accord on "all key aspects.

"Things have progressed, but not enough ... that we can reach an immediate deal," Fabius said in Paris. "We are firm. We want a robust deal with detailed checks.

China warned of failure and urged all sides to compromise. “If the talks are stuck, then all previous efforts to resolve Iran's nuclear standoff with the six major powers will have been wasted," said the rare statement by the Chinese delegation after Foreign Minister Wang Yi left Lausanne.

US President Barack Obama US Vice President Joe Biden and members of the national security team participating in a secure video teleconference from the Situation Room of the White House March 31, 2015 in Washington, DC, with Secretary of State John Kerry , Secretary of Energy Ernest Moniz and the US negotiating team in Lausanne, Switzerland, to discuss the P5+1 negotiations with Iran.

The U.S. administration of President Barack Obama had committed to meeting an end-March deadline for the outline political accord. Diplomats said they knew U.S. credibility was at stake after missing that deadline and getting a deal in the coming hours was crucial.

A senior Iranian negotiator said Tehran was willing to negotiate until the deadlock was resolved. "Iran does not want a nuclear deal just for the sake of having a deal, and a final deal should guarantee the Iranian nation's nuclear rights," the negotiator, Hamid Baidinejad, told reporters.

Hammond

Hammond, the US secretary of state, John Kerry, the Iranian foreign minister, Mohammad Javad Zarif, his German counterpart, Frank-Walter Steinmeier and the EU foreign policy chief, Federica Mogherini, stayed behind for a seventh day of talks in the Swiss lakeside town.

Germany stressed a political deal on a final Iran nuclear accord could still be reached amid intense negotiations in Lausanne, Switzerland between diplomats from Iran and six world powers (US, Russia, China, Britain, France and Germany).

German deputy foreign ministry spokeswoman Sawsan Chebli told IRNA in Berlin on Wednesday progress had been made in the talks and an agreement was 'still possible'.

We want to reach a deal quickly but I don't know how long it will still take, she added.

Chebli made clear however, she could 'not be 100 percent certain' that a deal could be reached after five days of what she described as 'serious negotiations'.

The Ministerial meeting between Iran and the Group 5+1 which started its work in the Swiss city of Lausanne on Wednesday ended for a breathtaking after two hours of discussion.

The two sides are negotiating a solution to the remaining disagreements and it is expected that they issue a final statement on resolution of key issues.