CAIRO – The Arab Spring, which began with an exuberant burst in Tunisia and Egypt and swept up protesters from North Africa to the Persian Gulf, is running into a brutal counter-revolution by hard-line regimes:

Syria was the latest country to respond to demands for political reform with a lethal crackdown last week.

In Libya, Moammar Gadhafi’s regime is still using deadly force to hold on to power despite a weeklong U.S.-led military campaign.

In Bahrain, a minority-led government invited its Arab neighbors to join a violent crackdown on demonstrators that has inflamed sectarian tensions.

In Yemen, talks over replacing a U.S.-backed dictator who has pledged to resign stalled over the weekend, with the regime warning that chaos would ensue if he leaves.

The Arab counter-revolution is in full swing, as entrenched regimes fight harder to survive and young, would-be revolutionaries struggle to maintain their momentum in the face of ever-more violent government reprisals.

“After the initial optimism of the Tunisian and Egyptian revolutions, we’ve seen a shift in the opposite direction, where protest movements are losing direction while regimes grow more confident that they can stay in power if they resort to excessive force,” said Shadi Hamid, a Middle East expert with the Brookings Institution.

“They’re willing to kill their own people if their survival demands it. The lesson they learned from Egypt and Tunisia was, if you give too much to opponents too quickly, you’re pretty much done,” he said.

By some measures, the revolts already have been wildly successful, with dramatic shifts in a region where political life had stagnated for decades. Of the Arab League’s 22 member states, only the tiny island of Comoros is truly unaffected by the rebellions. Nearly all the others are facing some internal strife, from the modest list of demands submitted by the opposition in Mauritania to bloody, all-out war in Libya.

Most countries are somewhere in between, facing sporadic protests that occasionally lead to violence and arrests.

“The genie finally came out of the bottle after many years of sleep,” said Abdulkader al Guneid, 61, a Yemeni physician and pro-reform activist. “Every country has its own conditions and circumstances, but it’s an all-new era for the Arab world. Now the people are revolting and speaking out loud, criticizing their governments and standing up to corruption and dictatorship.”

The new spirit has been too much for some dictators to handle.

For now, the worst-case scenario is Libya, where rebels who once vowed “Victory or death!” had to be bailed out by Western forces and only now are taking advantage of coalition airstrikes to regain territory they had lost to Gadhafi’s forces.

Across the region, the complexities of the uprising go beyond common calls for elected leaders, jobs and effective governance. In many countries, the clamor for political and economic reforms is tied to long-standing internal conflicts that could seep into the rest of the region if left unchecked. Sectarian strife, Islamic militancy, tribalism and poverty are all potential spoilers to democratic progress.

Ripple effects also have affected the Arab states’ neighbors:

The Turks are fearful that Kurdish uprisings in Iraq and Syria will inflame their own disgruntled Kurdish minority.

The Iranians support Shiite Arab demands but send forces to crush pro-reform demonstrations at home.

And the Israelis are sounding alarms that hostile Islamist extremists will seize power in the upheaval.

The countries now past the street-protest phase face major challenges. Even newly “liberated” Tunisia and Egypt are struggling to fill leadership vacuums while under interim military rule.

In Tunisia, the small North African state where the overthrow of a 23-year dictator in January set off the regional unrest, few vestiges of Zine el Abidine Ben Ali’s regime have been dismantled. Many Tunisians say that allies of the former regime continue to exert control over the media and that former members of the hated special police have merely been reassigned to other government posts.

Protests against poor working conditions at state-owned businesses have continued, and last week security forces arrested several demonstrators in the first significant crackdown on free speech since the revolution.

“All of these are worrying signs,” said Rashid Khalidi, the Edward Said Professor of Modern Arab Studies at Columbia University. “But these revolutions, if they’re going to succeed, are going to face a lot more difficulties than they already have.”