Iran and world powers are almost certain to miss Monday’s deadline for a deal to resolve the country’s twelve-year standoff with the West over its nuclear ambitions. The most likely outcome of the talks is an agreement to continue the talks.

The obstacles to a resolution are formidable.

Although Iran denies it seeks nuclear weapons, the capacity to build them could deter its adversaries in the region, including Israel and Saudi Arabia.

Having seen two of its neighbors — Afghanistan and Iraq — invaded by the United States in the last decade, Iran feels insecure. It also remembers that those leaders who gave up their weapons of mass destruction — Iraq’s Saddam Hussein and Libya’s Muammar Gaddafi — were later toppled with Western support anyway while nuclear states, such as North Korea, live without fear of being attacked.

For the West and its allies in the Middle East, a nuclear Iran is no less menacing. It would pose a genocidal threat to Israel, a country Iranian leaders have repeatedly threatened to eradicate, and could prompt its main rival, Saudi Arabia, to seek a nuclear weapons capacity of its own, thus triggering a nuclear arms race in one of the most volatile regions of the world.

There are political obstacles to a deal as well.

Republicans in the United States, who recently won control of Congress, are likely to oppose any agreement that they believe contains too many concessions. But as Jeffrey Goldberg writes in The Atlantic, many of President Barack Obama’s Democrats are no less skeptical. Even Obama’s former secretary of state, Hillary Clinton, who is the Democrats’ most likely presidential candidate for the 2016 election, has sounded more hawkish than her party leader on the issue.

Within Iran, hawks are critical as well, writes Mohammed Ayoob, a professor emeritus of international relations at Michigan State University, for openDemocracy.

They include elements of the Revolutionary Guard as well as hardline clerical and nonclerical factions that do not trust that President [Hassan] Rouhani and, especially, his foreign minister, Javad Zarif, who is the leading Iranian negotiator, are committed to or capable of protecting Iranian national interests especially in the nuclear arena. They believe that the Rouhani-Zarif team is likely to sacrifice Iran’s long-term goals at the altar of a short-term deal […] that could add to their popularity at home.

However, Rouhani, a relative moderate, was elected last year in order to get Iran relief from the economic sanctions that world powers imposed on his country to get it to negotiate. As Ayoob puts it, “the legitimacy of the regime has become tied to the lifting of sanctions in the eyes of the Iranian population.” If the talks collapse, it could set off popular unrest in Iran. If they succeed, it could prompt a crisis within the ruling elite.