Yemen's President Ali Abdullah Saleh speaks during an interview with media, in Sanaa on May 25, 2011.

© 2011 Reuters

There may be a silver lining to the recent diplomatic incident in Yemen, in which pro-government mobs blockaded U.S., European and Arab ambassadors inside an embassy as they waited -- in vain -- for President Ali Abdullah Saleh to sign a deal to relinquish power.

The ambassadors were unharmed, but perhaps their brush with the government's heavy-handed tactics will serve as a wake-up call. After witnessing their diplomats essentially held hostage by a regime they bankroll, the United States, the European Union and Gulf states should respond to Saleh's abusive behavior by freezing security assistance and seeking action by the United Nations Security Council.

We don't know whether Saleh engineered the siege to give diplomats a preview of the mayhem he claims would ensue if he were forced from power. If so, he is playing with fire. Since the embassy blockade, scores of fighters have been killed in clashes between Saleh's forces and opposition militiamen. A show of anarchy could quickly become reality in a country where many people are armed and desperate and the rule of law runs shallow.

Gangs doing the government's dirty work are nothing new in Yemen. Since February, security forces and pro-government assailants have killed at least 146 people in repeated attacks on peaceful protesters seeking to end Saleh's 33-year grip on power. Human Rights Watch has documented how, in many cases, these gangs opened fire or struck protesters with clubs and stones as security forces either stood by or facilitated the attacks.

Yemen's donors, including the U.S. and the EU, have deplored the violence and urged Saleh to step down. But they have failed to ratchet up the pressure by officially suspending the hundreds of millions of dollars in weapons and other security assistance they send to Yemen each year.

That includes more than $252 million that the U.S. has spent in the past two years alone to help Saleh's government take on Yemen-based al Qaeda in the Arabian Peninsula. But some governmental recipients of aid, such as the Central Security forces and the Republican Guards, have also been shooting peaceful protesters.

In lieu of firm action, donor countries have tried to sweet-talk Saleh into leaving on his own terms. Indeed, when ambassadors from the U.S., Kuwait, Oman, Britain and other EU countries gathered Sunday in the United Arab Emirates Embassy, they were preparing to head to the presidential palace to watch Saleh sign an exit deal that included blanket immunity not only for him but for relatives who run his security services.

Instead, hundreds of men surrounded the Embassy, brandishing guns and sticks, denouncing the exit pact and attacking the motorcade of the head of the Gulf Cooperation Council, the deal's chief negotiator. Hours passed before the government dispatched helicopters to airlift the ambassadors out. Saleh, for a third time, refused to sign the exit pact.

Hours later, his security forces stormed the house of a powerful sheikh in the capital, Sanaa, setting off days of armed clashes between government and opposition gunmen that have left scores of fighters dead and killed a half-dozen key tribal leaders as they were trying to negotiate a cease-fire. Elsewhere in the city, armed Saleh loyalists roam the streets, setting fires and assaulting alleged opposition members with impunity. "Fear is everywhere," one activist texted me. "It is like the gangs of New York in the (19th) century."

Before the crisis deepens, the U.S., the EU and their Arab allies should jointly freeze all security-related assistance and weapons sales to Yemen until authorities stop the violent crackdowns, conduct independent investigations into the attacks, prosecute suspected perpetrators, and compensate victims.

They also should jump-start discussions on bringing Yemen before the U.N. Security Council for possible sanctions. And they should press the U.N. Human Rights Council, which begins meetings in Geneva on Monday, to stop stalling on holding a special session that would specifically deal with Yemen.

If talks resume on an exit deal, negotiators should revoke all promises of immunity for serious human rights violations, which seem only to have encouraged Saleh's forces to continue unlawful attacks on protesters.

Yemen's donors and neighbors are right to be deeply concerned about the Yemen-based branch of al Qaeda and to question whether the group will benefit from a security vacuum after Saleh leaves office. But a foreign policy based solely on security concerns is bound to fail by alienating local populations.

As President Obama said last week, "Failure to speak to the broader aspirations of ordinary people will only feed the suspicion that has festered for years that the United States pursues our interests at their expense."

If the U.S., the EU and Gulf states don't stop training and arming a regime that kills peaceful protesters to stay in power, they risk stoking the flames of extremism rather than fostering Yemen's democratic development. The consequence could be far more problematic than a brief blockade of diplomats.