On Wednesday, Foreign Minister Mohammad Javad Zarif of Iran said that his country would “definitely greet Saudi Arabia with open arms” — but only if it prioritized friendly relations with neighbors over purchasing weapons from the United States.

Iran has long sought to pull Saudi Arabia away from the United States and Israel. But it was the lack of an American military response to the strikes on Saudi oil facilities that appeared to have created an opening.

“There are cracks in the armor suggesting Saudi Arabia is interested in exploring a new relationship with Iran,” said Philip Gordon, a former White House coordinator for the Middle East. “The worst outcome for the Saudis is to move to a confrontation with Iran expecting the U.S. to support them and find out they won’t.”

He added, “This administration has shown it’s not really ready to take on Iran.”

Top officials from Kuwait and the United Arab Emirates, Saudi allies which could suffer if open conflict broke out, have spoken publicly of the need for diplomacy to reduce tensions and have made their own efforts to reach out to Iran. The Emirates has held direct maritime security talks with Iran, and has pulled back from the war in Yemen, where it is allied with the Saudis in a battle against the Iranian-backed Houthi rebels.

If Saudi Arabia joins Kuwait and the Emirates in reaching out to Iran, it could undermine the Trump administration’s effort to build an international coalition to ostracize and pressure the Iranians.

“The anti-Iran alliance is not just faltering, it’s crumbling,” Martin Indyk, a distinguished fellow at Council on Foreign Relations and a former senior diplomat, said Thursday on Twitter. “MBZ has struck his deal with Iran; MBS is not far behind,” he said, referring to the Emirati crown prince, Mohammed bin Zayed, or MBZ, and the Saudi crown prince, known as MBS.

He also noted that Mr. Trump’s most hawkish anti-Iran adviser, John R. Bolton, had left the administration, Prime Minister Benjamin Netanyahu of Israel is fighting for his political life and Mr. Trump has shown a willingness to talk directly to the Iranians.