Oil-rich Kuwait, a key U.S. ally in the Persian Gulf, is deeply divided as its braces for a parliamentary election Saturday that's widely expected to produce a resounding victory for the ruling family and intensify political turmoil in the region.

With opposition groups threatening to boycott the polling after the emir, Sheik Sabah al-Ahmad al-Sabah, decreed a change in voting rules to weaken the opposition, the election could trigger a sharp escalation in pro-democracy forces' opposition to the monarchies of the region, including neighboring Saudi Arabia, the world's leading oil exporter.

The swelling political crisis in the emirate in the northern gulf is seen as the greatest threat to the country since it was liberated from Iraqi occupation by U.S.-led forces in February 1991.

The core of the crisis is a power struggle between Sabah, who appoints the government, and a 50-seat Parliament, the only elected national assembly in the gulf establish in 1962.

"The result is a showdown between the ruling Sabah family and ever-larger and increasingly assertive segments of the Kuwaiti population," said Kristian Coates Ulrichsen, co-director of the Kuwait Research program at the London School of Economics.

"The country has long been at the forefront of democratic evolution in the gulf. Kuwaitis are intensely protective of their constitutional and political rights and will oppose any renewed attempt to water them down.

"With neither the ruling family nor the opposition in any mood for compromise, there seems little prospect for a negotiated way out of the impasse," she said.

"The coming months will hold important lessons for the future of monarchy in the region more generally.

"For they will signify if ruling families are willing voluntarily to cede meaningful levels of control to elected institutions, or whether expressions of popular support for reforms will be resisted and, as in Bahrain, violently suppressed."

The Saudis have largely kept the lid on its domestic opposition, including a Shiite majority Riyadh has linked to arch-rival Iran. But the neighboring island state of Bahrain has been gripped by violence, including bombings, involving its Shiite majority and Saudi-backed security forces for more than a year and remains a powder keg.

The United Arab Emirates, another major gulf oil producer, blames protests by pro-democracy forces it's experiencing on Islamic extremists, a suggestion that diplomats in the region see as a gross exaggeration.

In Kuwait, there have been major street protests by the opposition, comprising Islamists, nationalists and liberals, demanding the repeal of the emir's new election law even though the government banned such gatherings in early October when Sabah, whose family has ruled for 250 years, dissolved Parliament.

On Oct. 21, Kuwait was rocked by some of its worst unrest in recent times as tens of thousands of people were dispersed by tear gas, stun grenades and baton-charges.

Opposition leaders have urged voters to boycott the election to foil "government plots" against the emirate's historic 1962 Constitution, the first proclaimed in the gulf.

Official repression in Kuwait is pretty mild by regional standards. But amid the so-called Arab Spring uprisings that have toppled Arab dictators in Egypt, Tunisia, Libya and Yemen since early 2011, Kuwaitis' patience is wearing thin.

Amid police crackdowns, resentment against the 85-year-old emir has been steadily building up and major protests are planned for Saturday.

Kuwait's turbulence began in the summer of 2011 with demands for the resignation of the prime minister, the emir's nephew. Things escalated in September over a massive corruption scandal in which 16 members of Parliament allegedly were paid large sums to support government policies.

When the constitutional court blocked attempts to question the prime minister, protesters stormed the assembly.

In November, Sabah dissolved Parliament, as he'd done five times previously. A new assembly was elected in February this year with the opposition tribal and Islamist candidates winning by a 34-seat landslide.

On June 20, Kuwait's highest court annulled the results and reinstated the previous assembly.

The emir dissolved that Parliament as well Oct. 7 and issued a decree reducing the number of votes per citizen from four to one, a move that favored the ruling family and its allies.

Opposition leader Musallam al-Barrak, addressing the emir with unprecedented bluntness, declared, "We will not allow you, your highness, to take Kuwait into the abyss of autocracy."