WASHINGTON: In struggling to keep pace with the Arab spring the United States has increasingly had to balance its democratic ideals with its long-standing interests in a complex and crucial region.

The uprisings have rapidly reshaped the political landscape, with former allies turned to liabilities when their people demand change and hopes for eventual rapprochement dashed as US foes drift further beyond the pale.

In September, President Barack Obama welcomed Hosni Mubarak as a trusted ally to the White House for Israeli-Palestinian negotiations. Six months later he hailed the strongman's fall, saying “the people of Egypt have spoken.” From the earliest days of the first uprising in Tunisia, Washington has struggled to keep up with events, as each revolt presented its own unique set of problems and all seemed to reveal diminishing US influence.

“It's not America that put people into the streets of Tunis or Cairo - it was the people themselves who launched these movements,” Obama said in a May address on the Arab spring, adding his government had to act with “humility.” But his administration has failed to resolve important contradictions at the heart of its response.

When Libyan strongman Moamer Qadhafi opened fire on his own people, the United States called on him to step down and joined a Western coalition air assault on his isolated regime.

But when Syria's Bashar al-Assad launched a similar crackdown on protests, the administration hesitated. It has condemned the violence, but is yet to call on Assad to resign, instead urging him to lead a political transition.

“We have imposed additional sanctions on the regime, including on President Assad and his inner circle,” White House spokesman Jay Carney said.

“We stand by the Syrian people, who have shown tremendous courage in demanding dignity and a transition to democracy. President Assad now has a choice. He can lead the transition or he can get out of the way.”

Officials have said that every case is different, noting that the Libyan intervention came as Qadhafi's troops neared the rebel stronghold Benghazi, vowing to annihilate the opposition in the country's second largest city.

But there has been no similar explanation for the administration's silence on Gulf monarchies like Saudi Arabia, Kuwait and the United Arab Emirates - authoritarian states that provide one seventh of US petroleum imports.

“To some degree, Saudi Arabia is the biggest obstacle in the US push for democratic change in the region,” Robin Wright, author of an upcoming book on the Arab spring, told NPR radio.

“It has not only backed Bahrain's repression, it is trying to mobilize an alliance of Arab states that will stand up to the protesters. After years of tension with Syria, it would like to see, in some ways, the Assad regime stay in power because that is stability.”

Rather than press Gulf states - which are also seen as a bulwark against Iran's expanding influence in the region - Obama, in his May address, talked about “opportunities,” particularly of the economic variety.

Another US interest seen as vital - the security of close ally Israel - is also shadowing its response to the revolts. On the day Mubarak fell, Washington called on Egypt to preserve the Camp David peace treaty.

The United States must also tread carefully when it comes to Yemen, where anti-regime protests have diverted Yemeni troops from the battle against al Qaeda's feared local affiliate.

Ali Abdullah Saleh - now in Saudi Arabia recovering from an opposition attack on the presidential compound - has ruled for more than 30 years, but has also been a close US ally in the fight against Islamist militants.

Often, instead of trying to navigate the complexities of the region, Obama has painted in broad strokes, comparing the Arab spring to the blossoming of democracy in Latin America and Eastern Europe over the last 30 years.

“For all the challenges that lie ahead, we see many reasons to be hopeful,” he said in his May address.

But Marina Ottaway, director of the Middle East Program at The Carnegie Endowment for International Peace, said the region was seeing yet another “rhetorical statement” instead of new policy.

Obama's speech did “not outline a policy, but a vision - that of a democratic and prosperous Middle East - which of course is not new,” she said.