BEIRUT — Lebanese officials insisted Friday on the return home of Prime Minister Saad Hariri from Saudi Arabia, and the leader of the militant group Hezbollah said the Saudis had “declared war” on Lebanon by holding Hariri against his will.

The U.S. added its voice to those urging that Hariri be allowed to return to Lebanon. A political crisis has gripped the country and shattered the relative peace maintained by its coalition government ever since his stunning announcement Nov. 4 from the Saudi capital that he was resigning.

The announcement from the Saudi-aligned Hariri jolted Lebanon and thrust it back into the regional rivalry between Saudi Arabia and Iran. The move and exceptionally strong statements by the Saudis against Iran that followed have deepened the mystery about Hariri’s fate and led to rumors that he is being held in the kingdom against his will, despite his denials.

For the past year, Hariri has headed a coalition government that included members of the Iranian-backed Hezbollah militia. He cited meddling in Lebanon and elsewhere in the region by Iran and Hezbollah in his decision to step down, adding that Iran’s arm into the region will be “cut off.”

Saudi Arabia appears to want to see Lebanon headed by someone who would form a government without Hezbollah, perhaps believing Hariri has become too lenient toward the group.

In a message apparently aimed at the Saudis but which could easily include Iran, Secretary of State Rex Tillerson cautioned against using Lebanon as “a venue for proxy conflicts.”

If Hariri wants to step down, Tillerson said, he needs to “go back to Lebanon” and formally resign, “so that the government of Lebanon can function properly.”

Lebanese President Michel Aoun told Saudi Charge d’Affaires Walid al-Bukhari on Friday that the manner in which Hariri resigned “was unacceptable,” a Lebanese official said, speaking on condition of anonymity in line with regulations.