The head of the UN's nuclear watchdog is in Tehran on what's being described as a "cautiously optimistic" visit. The Iranians seem to be playing it even safer and calling it a "goodwill gesture".

Both sides are holding their cards close to their chest. There hasn't been an International Atomic Energy Agency (IAEA)  director-level visit to the country since 2009.

Unusual for a visit of this nature, Yukiya Amano was travelling on Monday without a press officer, no press conference has been announced in Tehran, and very little information has been a given as to what the talks may be about.

Detail is scarce and secrecy seems to be the order of the day.

The reason why may be quite simple: oil.

Iran is facing perhaps the toughest embargo yet, and on July 1 it faces a European Union ban of its exports.

Iran is the second largest exporter of crude oil in the trade, according to the oil body OPEC.

If it can't get its oil out, the price of crude is likely to skyrocket globally and have a local impact. Iran's economy is oil driven, and if the embargo lasts long enough, it will have a significant impact on the country.

What Western diplomats are hoping is that the threat will mean that Iran will soften its negotiating position.

Permanent damage

If Iran has to cut crude oil production, according to experts, it may never get back to the peak levels it has so far enjoyed.

It's not as simple as turning the tap off. By cutting production you do permanent damage to oil production levels.

All of this overshadows the visit by Amano.

He might be hoping that Iran agrees to more inspections of its facilities, because of oil embargo threat.

But Iran has a trump card - oil prices. Losing Iranian oil to the world market means the price will go up.

That means those nations with strategic oil reserves may well have to dip into them and supply the market. A drastic measure. It becomes a game of who blinks first.

But neither Iran or the West want it to come to that.

If this is the case, then it's no wonder these talks have been shrouded in so much secrecy.

With so much at stake, a loose word or statement here or there could derail the whole process.

There has always been suspicion on both sides.

Iran wants to be treated with respect and not threatened by the West over its nuclear programme and has shown willing in the past.

Iran's argument is that it has signed the Nuclear Non-Proliferation Treaty, it has allowed inspectors in the past and is now willing to talk again. It has also insisted time and time again that its programme is for purely civilian purposes.

These are things the only other country to possess nuclear weapons in the Middle East, Israel, has not done, as Iranians like to point out.

Comparison with Israel

Israel has never had IAEA inspections. It has not signed the Nuclear Non-Proliferation Treaty and has never had to give public assurances  about the security of its arsenal.

Of course all of those things are a little difficult when you don't confirm or deny the existence of your nuclear weapons.

Add that to the fact its Israeli hawks who are leading the charge when it comes use of force on Iran, and the whole thing becomes incredibly politically charged. That we have seen time and time again.

It's for those reasons that I can understand why Tehran is reluctant to trumpet Amano's visit.

Iran and the West have been here before.

There is little trust on both sides and the atmosphere has been sullied with claim and counterclaim.

That's why the language is so important. "Cautious optimism" and "good will gesture" are words we have not heard before.

Monday's visit, whether a  decision is reached or not, is not definitive. Talks continue in Baghdad on Wednesday with the UN Security Council plus Germany.

If movement is to come, then perhaps, it will come in the upcoming days and weeks.

"Cautiously optimistic" is then one way of describing the atmosphere.  But when so little detail is available, perhaps that's all we can hope.