WASHINGTON — Five years after President Barack Obama vowed to expand U.S. relations with the Arab world and the broader Middle East, his administration is under fire from allies worried that the United States is scaling back its historic role as a power broker and peacemaker despite growing turmoil across the region.

With a bitter power struggle intensifying between Iran and Saudi Arabia and widening crises in Syria, Iraq, Libya and Egypt, Washington’s relative lack of influence and involvement has become a diplomatic problem and may be contributing to a growing threat from Islamic extremists, diplomats say.

Senior officials in Saudi Arabia, Turkey and Israel all have complained about what they view as an American retrenchment after the wars in Iraq and Afghanistan, with some leaders already beginning to chart policies more independent of Washington than in the past.

Secretary of State John F. Kerry sought to ease those concerns Friday, insisting in a foreign policy address during the World Economic Forum in Davos, Switzerland, that “it is a myth that we are pulling back or giving up or standing down. … Nothing could be further from the truth.”

Disputing charges that the Obama administration is shedding commitments, Kerry said that “you cannot find another country that is so engaged, that is partnering with so many Middle Eastern countries on so many fronts.”

Misperceptions may be based “on the simplistic assumption that our only tool of influence is our military and that if we don’t have a huge troop presence somewhere or we aren’t brandishing an immediate threat of force, we are somehow absent from the arena,” he said.

Allies’ worries have grown as the White House has struggled with the messy aftermath of the so-called Arab Spring uprisings in 2011, a period that saw autocrats toppled but led to the nearly 3-year-old civil war in Syria, mounting strife in Egypt, a war in Libya and other problems. More recently, al-Qaida-linked fighters have seized territory and cities in Iraq.

Middle Eastern leaders are unsettled as well by Obama’s promise to “rebalance” U.S. foreign policy to put more emphasis on East Asia and the Pacific. Despite White House denials, they believe Washington is pulling back from the Middle East.

Kerry said U.S. priorities in the region were to curb Iran’s nuclear development, to break the bitter stalemate in Israeli-Palestinian peace talks, and to help end the Syrian war through negotiations. Clear progress has been made so far only with Iran, which agreed Jan. 20 to a six-month interim deal that called for a partial lifting of Western sanctions in exchange for a partial freeze on most of its nuclear enrichment work.

Turkey, Saudi Arabia and other Persian Gulf states have urged Washington to do more to help rebel militias fighting to oust Syrian President Bashar Assad, and they were alarmed in September when the White House backed off its threat to use airstrikes to punish Assad’s government for using chemical weapons.

Although Syria agreed to surrender its chemical arms arsenal and production facilities to United Nations-backed inspectors, Obama’s refusal to use military force was seen by some Israeli officials as undermining U.S. credibility.

Saudi leaders have been especially critical of Washington. Their frustration has become so public that the kingdom turned down a seat on the U.N. Security Council partly to protest inaction on Syria.

Gulf states are fearful that the White House is seeking not just a deal to limit Iran’s nuclear efforts, but a broader rapprochement with Tehran. Some gulf officials warn that they may bolt from longtime security agreements with the U.S. and work out their own deals with Iran if they see Washington move toward an accommodation with Tehran.

Robert M. Danin, a former senior U.S. diplomat in the Middle East, said the administration had narrowed its interests in the region. It continues to focus on international terrorism and arms proliferation, he said, but is less willing than before to intervene in domestic crises, such as the recent crackdown on antigovernment protesters in Egypt.

“Now they say, ‘We won’t get involved in this or that,’” said Danin, a senior fellow at the nonpartisan Council on Foreign Relations. “That’s a major shift.”

One result has been new challenges for Washington.

Saudi Arabia and Qatar have provided weapons to some Syrian rebel groups, for example, that U.S. officials say are linked to al-Qaida. And Saudi Arabia has committed billions of dollars to help Egypt’s military government in ways “that have really made our policy tools less effective,” said Michael Singh, managing director of the Washington Institute for Near East policy and a former aide in the George W. Bush White House.

Administration officials insist Obama isn’t neglecting America’s traditional allies or their problems.

In his speech Friday, Kerry said the administration was working with Saudi Arabia and the United Arab Emirates on a long-term security framework for the region, and was helping countries that saw revolutions since the Arab Spring, including Egypt, Tunisia and Libya.

The efforts “have the potential to reshape the Middle East and could even help create the foundations of a new order,” Kerry said.

He said the United States was limiting its efforts in Syria largely to diplomacy because it believes that “there is no military solution,” and because the American public is strongly against a military intervention.

“There are people who would love to see America fight their war for them,” Kerry said. “But that is not their choice.”

