Iran's Supreme Leader Ayatollah Ali Khamenei made the comments in a meeting with visiting Lebanese President Michel Suleiman, the official IRNA news agency reported.
"Iran believes the capability of all Lebanese groups should be at the service of (Lebanon's) power and unity to confront the danger of the Zionist regime," Khamenei told Suleiman, using a term Iranian officials often use to refer to Israel.
Suleiman, a Maronite Christian, was elected president in a May parliamentary vote after an 18-month standoff between the U.S.-backed government and the Hezbollah-led opposition.
Under Lebanon's power-sharing system the presidency is held by a Christian while other top posts are taken by Sunni and Shi'ite Muslims and members of the Druze sect.
"Holding talks among different Lebanese groups that are now led by the president is considered positive because Lebanon's bright future depends on national unity," Khamenei said.
Suleiman, a former army chief, was elected as part of an agreement brokered by Qatar in May to defuse the political crisis that had pushed Lebanon to the brink of civil war.
Tehran has often praised Hezbollah, which has formidable guerrilla army, for fighting Israel in a 34-day war in 2006. Israel has accused Iran of supplying weapons to Hezbollah but Iran insists it only provides moral and political support.
"Lebanon as a friendly and brotherly country in the region will always enjoy Iran's spiritual support," Parliament Speaker Ali Larijani told Suleiman, Iran's ISNA news agency reported.
Khamenei also said Iran would "always be on Lebanon's side" and said he hoped talks during Suleiman's visit would strengthen ties.
Suleiman, who arrived on Monday, also met Iranian President Mahmoud Ahmadinejad during his two-day visit.
(Reporting by Zahra Hosseinian; Writing by Edmund Blair; Editing by Dominic Evans)
