BEIRUT — Lebanon’s new president got a red carpet welcome yesterday, but was quickly thrust into the political thicket as Hezbollah’s leader warned against any efforts to disarm his Iranian-backed guerrilla group.

Sheik Hassan Nasrallah delivered his stern message after military bands and an honor guard saluted President Michel Suleiman on his first day on the job.

Mr. Suleiman, the former army commander, was a consensus candidate agreed on by both Hezbollah and its pro-Western political foes, but he drew pointed comments from Sheik Nasrallah after saying in his inauguration speech Sunday that there should be a dialogue over Hezbollah’s arsenal.

The Shiite group has rejected demands it disarm, insisting its weapons are needed to protect Lebanon from Israel.

Sheik Nasrallah’s speech was his first since Hezbollah fighters seized several areas of Muslim west Beirut in several days of fighting this month, forcing the Western-backed Cabinet to agree to a political deal designed to give Hezbollah and its allies a veto over government policies.

The Hezbollah leader pledged to comply with a provision of the Arab League-brokered agreement that forbids the use of arms to achieve political gains. But he warned that the government shouldn’t try to use the military against Hezbollah and its allies.

“The resistance weapons should not be used to achieve political gains,” Sheik Nasrallah told thousands of supporters crowding a playground in south Beirut, speaking by videolink from a hiding place in fear of assassination by Israel.

At the same time, he said, “the state’s weapons should not be used to settle accounts with an opposition political party, or in favor of outside parties that weaken Lebanon’s strength and immunity in confronting Israel.”