CAIRO, Dec. 21 -- Iran and the world powers decided late last month to extend again the deadline for a comprehensive agreement on Tehran's controversial nuclear program to July, next year, the second such move this year.

The extension is perhaps the single most celebratable achievement after more than a year of on-and-off tough talks that still saw no major breakthroughs to a host of gaps between the two sides.

In the coming months, if without substantial compromise, it would still be a distant dream for Iran and the six-nation group, also known as the P5+1, to find enough common ground for a final deal before the time runs out again.

PROGRESS MADE IN 2014

As Iran and the P5+1 bloc (China, France, Germany, Russia, the Great Britain and the United States) have held numerous rounds of talks, they have also tried to implement a joint action plan reached between them late last year in Geneva, and the IAEA began its inspection and monitoring of the Iranian nuclear program so as to ensure that Tehran was actually cooperating.

According to an IAEA report, the Islamic Republic stopped the 20 percent Uranium enrichment, a technical step away from developing weapons-grade Uranium. It also halted major activities at the Arak heavy water and Plutonium reactor.

Iran also promised to build a plant which would convert the five percent enriched Uranium into an oxide, which cannot be utilized for further enrichment.

The United State and European Union (EU), in return, began to suspend some of the economic sanctions against Iran in such areas as the automotive sector, gold and precious metals trade, plane parts, and petrochemical exports.

Also, Tehran would get seven billion U.S. dollars in sanctions relief, in which 4.2 billion were from the Iranian oil sales revenue in frozen accounts.

With the moderate sanction relief, Iranian President Hassan Rouhani has made some progress in stabilizing the country's economy in 2014. He has brought inflation rate down from 39 percent to 17 percent. And the nation's economy is expected to grow at 1.5 percent after two years of recession, according to the International Monetary Fund's data.

WHAT DIVIDES THEM?

The most hard-to-crack problems now divide the negotiators are how much nuclear capability Iran can keep, and the steps to lift West-imposed sanctions against Tehran.

The Western powers want Iran to massively cut its Uranium enrichment activities, including decreasing the number of centrifuges to a few thousands. Latest media report said the Obama administration agreed to allow Iran to operate 6,000 centrifuges, up from a previously reported ceiling of 4,000 several weeks ago.

Iran has 9,400 operating centrifuges and roughly 10,000 others that are not in operation, and it insists that it must maintain its current level to provide fuel for electricity and other peaceful purposes. Iran's Supreme Leader Ayatollah Ali Khamenei said that his country should have no less than 19,000 centrifuges, which is a "red line."

Meanwhile, the fate of the unfinished Arak heavy-water reactor has also been a concern for the West. The reactor can produce plutonium for bombs, while Tehran says it is only intended for medical and agricultural research.

Washington and other Western capitals demand that Iran re-engineer Arak to a light-water reactor that makes only limited amounts of plutonium. In contrast, the Iranians' reengineering proposal is reversible, and is opposed by the United States.

On sanctions, Iran wants them to be lifted immediately while the West says the sanctions should be removed gradually in the event of Iranian non-compliance.

A PRODUCT OF DISTRUST

Although it is still foggy to see whether these gaps could be removed or not as negotiators gather for talks in the coming months, yet one thing is certain that Iran's nuclear issue is in fact a product of distrust.

In 1953, for oil interest, the United States, with the help of the British, staged a coup in Iran that toppled the government of Mohammed Mossadegh, and restored the rule of Shah Mohammad Reza Pahlavi.

However, in 1979, the Shah of Iran, who was considered heavily dependent on Washington's support, was ousted in the Islamic revolution, which led to a U.S. hostage crisis, a major contributing factor that turned Jimmy Carter into a one-term president.

The 1979 revolution was also the starting point from which Tehran and Washington have begun to take each other as adversaries, while their relations constantly deteriorated in the years since.

Before President Obama and then-newly-elected-Iranian President Hassan Rouhani spoke over the phone in September, last year, and agreed to accelerate the nuclear talks, there was no direct contact between the leaders of the two countries since the hostage crisis. Thus it is easy to understand why there are so many hard-liners in the two countries prime for a fight in case the talks fail.

DIFFICULTIES LIE AHEAD

Significant differences and long-lost trust have suggested that in the future talks, negotiators have to cope with unprecedented international and domestic pressure and to exercise political wisdom in order to deliver a comprehensive nuclear deal.

Just last week, U.S. and Iranian negotiators held a two-day meeting in the Swiss city of Geneva to prepare for wider talks on how to end the long-standing dispute. Iran's deputy foreign minister Abbas Araqchi said the talks were "very useful and helpful," while the U.S. team made no comment.

In fact, if the nuclear negotiations were to go broke, no one would be victorious, and the first to suffer is Iran.

Without a nuclear agreement, the moderate Iranian government could face a shrinking popularity internally, and Ayatollah Khamenei may withdraw its supportive positions for the talks. In the mean time, Iran's economy would continue to be hammered by the sanctions imposed by the Western powers, especially at this moment when global oil prices are plummeting.

As for the United States, President Obama's diplomatic legacy will suffer a major blow if the talks fail to produce a comprehensive agreement.

Moreover, Washington may have to deal with a more hawkish and uncooperative Iranian government and a much more complicated security situation in the Middle East, which has been engulfed by conflicts and the rise of Islamic State militant group and other likewise terrorist organizations.

Accomplishments always come with a price. It is no doubt that when the negotiators gather under the same roof again next year, they have to entertain the price they are willing to pay for a final deal. And one thing for sure is that if they are courageous enough to make some key compromises, their bravery will be rewarded far more than they can anticipate.

key compromises, their bravery will be rewarded far more than they can anticipate.