Kerry seeks to seal historic Iran nuclear accord

But diplomats on both sides say major differences remain

US Secretary of State John Kerry will try and seal a historic deal with Iran today that would curb its nuclear programme in exchange for relief from painful sanctions.

But just days ahead of Tuesday's deadline for Iran and six major powers to nail down the accord they hope will end a 13-year standoff, diplomats on both sides said Friday that major differences remain.

As a result, the June 30 target date may slip -- if only for a few days -- setting the stage after almost two years of hard bargaining for yet another bruising and lengthy round of talks.

"Some major problems exist which are still blocking the work... But in other areas we have made good progress," Iranian Deputy Foreign Minister Abbas Araghchi told state television yesterday from Vienna, where the talks will be held.

"Overall, the work is moving ahead slowly and with difficulty," he added.

This was echoed by a Western diplomat, who said that several key issues including a stalled UN probe into Iran's past activities and the timing of sanctions relief remain "extremely problematic".

"The most difficult issues need to be resolved in the coming days: transparency, inspections, PMD (possible military dimensions of Iran's nuclear programme), sanctions... On the major issues there is major disagreement," the diplomat said.

A senior State Department official said Kerry would meet Iranian Foreign Minister Mohammad Javad Zarif today morning "to discuss the ongoing P5+1 nuclear negotiations".

A deal, it is hoped, would put an end to a crisis dating back to 2002 that has threatened to escalate into war and has poisoned the Islamic republic's relations with the outside world.

Even if negotiators manage a deal, it will be closely scrutinised by hardliners both in Iran and the United States, as well as Iran's regional rivals Israel, widely assumed to have nuclear weapons itself, and Saudi Arabia.

In return for downsizing its activities and allowing closer UN inspections, Iran, which denies wanting nuclear weapons, would see the progressive lifting of UN and Western sanctions that have choked its economy.