Iranian President Mahmoud Ahmadinejad arrives in Beirut on Wednesday for a controversial visit, the highlight of which will be a tour of Lebanon's volatile border with his arch-enemy Israel.
The hardline leader during his two-day official trip -- his first to Lebanon since he became president in 2005 -- will meet with his counterpart Michel Sleiman as well as Prime Minister Saad Hariri and parliament speaker Nabih Berri.
He will also attend a rally in the Lebanese capital organised on his behalf by the Shiite militant group Hezbollah, considered a proxy of Iran.
Hezbollah leader Hassan Nasrallah, whose party fought a devastating war with Israel in 2006 and is blacklisted as a terrorist organisation by Washington, is expected to attend the rally, though it is not known whether he will do so in person or via video link.
He has not appeared in public for more than two years.
But the most anticipated and controversial part of the visit will be on Thursday, when Ahmadinejad is scheduled to tour several villages along Lebanon's southern border with Israel.
The region was largely destroyed during the 2006 war between Hezbollah and the Jewish state and was rebuilt with the help of Iranian money.
Members of the pro-Western parliamentary majority in Lebanon have described the border visit as a provocation and a defiant message to Israel that Iran's borders extend to Lebanon.
The United States and Israel have also reacted negatively with the Israeli government saying it could undermine regional stability.
But beyond that, the visit comes at a pivotal moment in Lebanese politics. Hezbollah and Hariri's camp are locked in a standoff over unconfirmed reports that a UN-backed tribunal is set to indict members of the militant party for the 2005 murder of Hariri's father, ex-premier Rafiq Hariri.
Tensions over the tribunal have grown steadily in recent weeks, raising fears of sectarian violence and the collapse of the national unity government, in which Hezbollah has two ministers.
Ahmadinejad's visit also comes at a time of high tension between Tehran and Tel Aviv over Iran's controversial nuclear programme.
"At stake is whether Ahmadinejad is coming to show support for Lebanon or whether he plans to use Lebanese territory as a springboard for his own interests," said Fadia Kiwan, head of the political science department at Beirut's Saint Joseph University.
"The Lebanese, and Hezbollah in particular, must fully take advantage of Iran's support but must also realise the limits of this support, that it's a double edged-sword," she added.
Ali Akbar Javanfekr, a senior aide to Ahmadinejad, told AFP that the Iranian president's visit was of "historical importance and would influence regional equations."
"The trip aims to consolidate the bilateral relations in several areas and it is within the framework of our strategic foreign policy with the regime in Lebanon that this visit has been planned," he said.
"There are also emotional ties between the two countries, apart from a long historical relation based on common religion and culture."
Ahmadinejad will be accompanied on his trip by Foreign Minister Manouchehr Mottaki and a delegation of businessmen from the private sector.
A number of agreements covering the energy and water sectors will be signed during the visit.
The Lebanese president will be hosting Ahmadinejad for lunch while the speaker of parliament is hosting him for dinner. Prime Minister Hariri will also be hosting him for lunch on Thursday.
In a speech at the weekend, Nasrallah called for a massive turnout to greet the Iranian leader and denied rumours that Ahmadinejad planned to throw a symbolic stone across the border at Israel.
"If President Ahmadinejad asks my opinion, I would tell him: 'A stone? You are capable of throwing more than a stone'," Nasrallah said.