Lebanon's interior minister tried on Wednesday to calm a dispute over a change in rules for entering the country, which some politicians feared reflects deepening influence of Iran and its ally Hezbollah.
The move by a state security agency allows entry for Iranians at the airport without their passports being stamped.
Caretaker Interior Minister Nohad Machnouk said that the directive from General Security also applies to Gulf Arabs, and that he would hold talks with Prime Minister Saad al-Hariri to decide within a few days whether to cancel the measure.
Lebanon's Shia Hezbollah movement and its allies emerged from elections in May with greater sway in parliament, part of a bigger picture of Iranian clout that the United States wants to counter.
The staunchly anti-Hezbollah Lebanese Forces, a Christian party, slammed the passport directive as an attempt to help Iran send more forces to neighbouring Syria or move money to Hezbollah despite U.S. sanctions.
Tehran and Hezbollah give critical support to the Syrian military in the seven-year conflict next door.
The General Security agency, which oversees airport security, has defended its move as normal and said Iranians' entry cards would be stamped instead.
"This has political implications," Machnouk told a press conference after meeting the head of General Security. "Especially at this difficult time for Lebanon and the region, in terms of the American-Iranian confrontation and U.S. sanctions."
He said the directive covered nationals from Iran and countries in the Gulf Cooperation Council, without spelling out whether it had included both initially.
Machnouk added that the United States, many European countries and some Arab states had suspicions about people visiting Beirut and could assume they were coming for "training or contacting organisations that are internationally rejected".
Washington designates Hezbollah as a terrorist group and has tightened sanctions in recent months against people accused of doing business with it. The European Union classifies Hezbollah's military wing as terrorist.
Machnouk, a member of Hariri's Future Movement party, said he had the legal authority as interior minister to cancel the new measure.
"(This) is part of the political clashes that Lebanon does not need at this time," he added, as the western-backed Hariri tries to form the next coalition government.
Major General Abbas Ibrahim, who heads General Security, has defended the change as a normal procedure and said a database automatically registers all arrivals and departures.
He added that travellers in general have the right to ask not to get a stamp on their passport if it might cause them difficulties when going to another country.
"Unfortunately, some in Lebanon have a wide imagination," Ibrahim said in remarks to local daily al-Joumhouria earlier this week. Many European and Gulf countries refrained from stamping passports, the Shia official said.