is Iran's nuclear deal near ?

After years of disagreement and distrust, a deal between Iran and international powers over its nuclear program seems near as top diplomats flock to the site of ongoing talks.

U.S. Secretary of State John Kerry landed in Geneva early Saturday and went straight to the venue where talks are being held.

A day before, a Western official said that a deal was within grasp.

And at the beginning of Saturday's working meeting, the mood was still positive, a leading European Union diplomat told CNN on condition of anonymity.

The Iranians seem to share the sentiment. "Not bad," was the assessment of progress by an Iranian diplomat, who did not wish to be named.

The EU's foreign policy chief, Catherine Ashton continues to lead the talks with Iranian Foreign Minister Javad Zarif and his counterparts from other countries, the EU diplomat said.

She has briefed Kerry, who went on to meet with world's most powerful foreign policy chiefs. They have hastily made their way to Geneva, raising hopes that negotiators working on their behalf are close to an agreement with Iran.

Zarif said Friday there is wide agreement except for a couple of points, the semiofficial Iranian Students News Agency reported.

"Numerically speaking, perhaps 90% of progress has been made, but there (are) one or two issues which are of great significance," he said.

Kerry joins British Foreign Secretary William Hague, and French Foreign Minister Laurent Fabius. Chinese Foreign Minister Wang Yi will also attend, as well as his Russian counterpart, Sergey Lavrov.

Together, these diplomats represent the five permanent members of the U.N. Security Council plus Germany -- together known as the P5+1 -- which has been negotiating with Iran on its nuclear program.

Western powers want Iran to restrain technical advancements that could put it close to developing a nuclear weapon. Tehran wants economic sanctions that are strangling its economy loosened.

But Iran also insists it has the right to enrich uranium, saying that it will only be used for a peaceful nuclear energy program.

Tehran wants that written into the deal, which would likely cover a period of six months and ideally be a precursor to a more sweeping pact, diplomats said.

Western powers, on the other hand, prefer ambiguity on this matter. They don't want it written into the agreement. But if Iran states it has the right to enrich uranium, the West won't argue with it, the diplomats said.

Washington and its allies also only want to lift only some of the sanctions and leave some tough ones in place for now.

For years, Iran and Western powers have left negotiating tables in disagreement, frustration and at times open animosity.

But the diplomatic tone changed with the transfer of power after Iran's election this year, which saw President Hassan Rouhani replace Mahmoud Ahmadinejad.

Caustic jabs at the United States and bellicose threats toward Israel were a hallmark of Ahmadinejad's foreign policy rhetoric.

He lambasted the West over the economic sanctions crippling Iran's economy and at the same time, pushed the advancement of nuclear technology in Iran.

Rouhani has struck up a more conciliatory tone and made the lifting sanctions against his country a priority.

During a visit to the U.N. General Assembly in September, Rouhani's moderate approach raised hopes in the West of a thaw in relations with Tehran and progress in negotiations on its nuclear program.

Despite the sanctions, Iran today has 19,000 centrifuges and is building more advanced ones, according to Mark Hibbs, a nuclear policy expert at the Carnegie Endowment for International Peace.

Most world powers believe that Iran could not realistically build a usable bomb in less than a year, Hibbs said.

And Iran recently signed a deal with the International Atomic Energy Agency that agrees to give the U.N. nuclear watchdog agency access to long-unseen nuclear sites, including a heavy-water reactor in Arak.

Tehran is also a party to the Treaty on the Non-Proliferation of Nuclear Weapons, which requires it not to create nuclear weapons or enable other countries to obtain them.

Key U.S. allies in the Middle East and some Washington lawmakers still don't trust Iran.

They believe that by making concessions on sanctions, the United States and its allies are giving up important leverage against Tehran.

Saudi Arabia, Iran's nearby neighbor across the Persian Gulf, has lasting tensions with Tehran and has publicly derided the Obama administration's negotiating stance.

A bipartisan group of six senators urged the President's team to reject the proposed deal and accept only an agreement that better dismantles Iran's nuclear technology.

Israeli leaders, as well, would like to see the heat turned up on Tehran, not down. Defense Minister Moshe Ya'alon reiterated the point after a meeting with U.S. Secretary of Defense Chuck Hagel on Saturday in Israel.

"We think the deal that is on the table is a bad one and even if this deal is signed there will be a lot to do afterward to bring the Iranian regime face to face with the dilemma of the bomb or survival."

Israel has said that it reserves the right to defend itself militarily against an Iranian nuclear threat.

Israeli Prime Minister Benjamin Netanyahu has been adamant in his distrust of Tehran and his belief that sanctions are working and should get tougher.

"If you give it up now, when you have that pressure, and Iran doesn't even take apart, dismantle one centrifuge, what leverage will you have when you've eased the pressure?"

But President Barack Obama said that sanctions put in place during his administration had forced Iran to the negotiating table and easing them some could help move things forward.

The proposed deal would only "open up the spigot a little bit" on frozen revenue, while leaving in place the bulk of the most effective sanctions involving Iranian oil exports and banking.

The President also stressed that all options, including military strikes on Iran's nuclear facilities, remained on the table as far as the United States was concerned.