|Hassan Nasrallah asked politicians and citizens not to co-operate with investigations into Rafiq al-Hariri's murder [AFP]
Saad al-Hariri has arrived in Tehran for a two-day visit - his first trip to the Islamic Republic since becoming the Lebanese prime minister.
Hours before arriving in the Iranian capital, al-Hariri said Iran had a major role to play in his country, Iran's IRNA news agency reported.
"The Islamic Republic of Iran has a natural role in the region, especially in resolving crisis and strengthening stability in Lebanon,"he was quoted as saying.
The visit comes amid a tense political standoff between Hariri's pro-Western camp and the Shia Muslim movement Hezbollah, over a UN investigation into the 2005 assassination of Rafiq al-Hariri, al-Hariri's father and former prime minister.
A Lebanese ministerial source told the AFP news agency that al-Hariri hoped Iran would help to reconcile the two rival groups.
"This visit is important because of its timing at the time when Lebanon is in crisis because of the expected indictment of the Special Tribunal for Lebanon," the source said.
The tribunal is expected to implicate high-ranking Hezbollah officials in the murder, but the party has warned against that, prompting fears of sectarian unrest between al-Hariri's predominantly Sunni Muslim supporters and Hezbollah, which is backed by Iran and Syria.
"The Iranians will try to reconcile points of view between Hezbollah and Saad Hariri," the source said.
In return, al-Hariri would support Iran's "development of nuclear capabilities for civilian and peaceful purposes," the source said.
Lebanese officials hope a recent initiative by the leaders of Saudi Arabia and Syria, who back rival camps in Lebanon, will help prevent any escalation of violence.
Iran's endorsement of the Saudi-Syrian efforts is vital for their success.
"The framework of the Saudi-Syrian initiative is in place and its roadmap is there. Now the discussion is in its details," Okab Sakr, a parliamentarian close to al-Hariri, said.
Al-Hariri's visit follows a trip to Lebanon last month by Mahmoud Ahmadinejad, Iran's president, who stressed support for all Lebanese but also made a high profile tour of Hezbollah strongholds, highlighting the influence of Tehran's ally.
Tensions over the Rafiq al-Hariri investigation have already paralysed the unity government, which includes Hezbollah ministers.
Hassan Nasrallah, Hezbollah's leader, has urged all Lebanese to boycott the tribunal and vowed to block the arrest of any of his members.
He has also called on al-Hariri to repudiate the tribunal, which he described as an "Israeli project".
Source: Al Jazeera and agencies