On the eve of a self-imposed deadline, talks towards a landmark nuclear deal between Iran and six major powers have continued overnight, with both sides saying that more time might be needed.

Foreign ministers and officials from Iran and members of the P5+1 group - comprising Britain, China, France, Germany, Russia and the US - are gathered in Vienna to try to strike a deal with Iran by Tuesday night.

Asked in Washington about another "slip" beyond Tuesday's target date for an ambitious accord, aimed at ending a 13-year standoff with Iran, a White House spokesman said it was "certainly possible".

"July 7, July 8, we do not consider these dates as those dates we have to finish our job," the official told reporters.

"Even if we pass July 9, that will not be the end of the world, there will be another period for us to watch."

A dispute over UN sanctions on Iran's ballistic missile programme, as well as a broader arms embargo, are said to be among the main issues holding up the agreement before this latest self-imposed deadline.

"The Iranians want the ballistic missile sanctions lifted. They say there is no reason to connect it with the nuclear issue, a view that is difficult to accept," one Western official told the Reuters news agency on Monday. "There's no appetite for that on our part."

Separately, a senior Iranian official speaking on condition of anonymity told reporters in the Austrian capital that Tehran wanted a UN arms embargo terminated as well.

The Iranian official said his country had made "a number of concessions" but that a number of issues - few in number but "tough" - remained to be thrashed out at ministerial level.

Al Jazeera's James Bays, reporting from Vienna, said while there has been much progress in the talks, "gaps" still remain, which need "political decisions" among the countries involved.

"We are told by all sides that there are only a few remaining sticking points on the table," he said.

Previous deadlines missed

Having agreed to an interim deal in November 2013 following the election of Iranian President Hassan Rouhani, Iran and the P5+1 missed a July 2014 deadline to get a lasting deal, and then again last November.

In April, several days late, they managed to agree on a framework accord. A target date of finalizing this by June 30 was pushed back to July 7.
But by late Monday, it became clear there was still no light at the end of the tunnel despite progress in tidying up some of the details in what will be a complex and contentious agreement.

John Kerry, the US secretary of state, is under pressure to nail down the deal by Thursday in order to send it to the Republican-controlled US Congress for a 30-day review.

Under a new law, if the deal is reached after July 9, US legislators will have 60 days to vote on it, giving opponents who think the deal is too weak more chances to try to scupper the accord.

Building on the April framework, the P5+1 powers want Iran to sharply curb its nuclear programme to make any push to acquire an atomic bomb all but impossible, in return for sanctions relief.

Iran denies wanting nuclear weapons, saying its activities are purely for peaceful purposes.

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Both sides at the Vienna talks say that more time may be needed to thrash out a deal [Reuters]

Aljazeera