Israeli officials were trying to keep a low profile both in the media and in the field in order to prevent escalation of already high tensions along Israel's shared border with Lebanon, as thousands of Shiite supporters welcomed Iranian President Mahmoud Ahmadinejad in Beirut on Wednesday.

Israel's main efforts concentrated on the conveying of diplomatic messages to the Lebanese government via the U.S., France the United Nations, among them the demand to avoid provocations along the border.

Israel's stance, which has been clearly expressed over recent days, is that Ahmadinejad's visit proves that Lebanon is becoming more extreme, on its way to becoming an Iranian outpost. "Lebanon has joined the axis of extreme nations which object to the peace process and support terror," said a senior Israeli official involved in preparations for the two-day visit.

The official added that "Iran's president is visiting Lebanon like a commander coming to inspect his troops – Hezbollah terrorists – who serve as a wing of Iran's military in the region. Anyone who holds peace and freedom dear is watching this Iranian provocation with concern. Lebanon, which could have enjoyed peace and prosperity, has turned into the servant of the Iranian aggressor, led by Hezbollah."

Defense Minister Ehud Barak also remarked on the visit, saying that "Ahmadinejad's visit clearly reflects Hezbollah's growing dependence on Iran, and the fact that Lebanon has gradually ceased to be a normal country, where its interests govern its policy, and has somewhat turned into a tool maneuvered by external powers," he said, adding that the Israel Defense Forces and Israel's intelligence agencies were keeping "eyes open."

Meanwhile, the U.S. also expressed concern over Ahmadinejad's two-day visit to Lebanon, saying support for Hezbollah militants undermines Lebanese sovereignty.

Ahmadinejad is continuing his "provocative ways," the White House said in a statement Wednesday.

"He continues his provocative ways, even as he leaves his county in further economic stress and turmoil as a result of his actions that have led to international sanctions that are having a great impact," White House spokesman Robert Gibbs said.

Gibbs was referring to UN Security Council sanctions placed on Iran over its alleged refusal to come clean about its nuclear activities suspected by the West as intended to develop a bomb. Tehran says the program is purely for peaceful purposes.

"We reject any efforts to destabilize or inflame tensions within Lebanon," U.S. Secretary of State Hillary Clinton said. "We would hope that no visitor would do anything or say anything that would give cause to greater tension or instability in that country."

Allies of the Western-backed, mainly Sunni parties that hold a slim majority in the Lebanese parliament also showed their worry.

A group of 250 politicians, lawyers and activists wrote an open letter to Ahmadinejad, criticizing his support of Hezbollah.

"Your talk of 'changing the face of the region starting with Lebanon' and 'wiping Israel off the map through the force of the Islamic Resistance in Lebanon' ... makes it seem like your visit is that of a high commander to his front line," the letter said.

In Tripoli, a mainly Sunni city in the north, posters have gone up in recent days showing Ahmadinejad's face crossed out, above the words: No welcome to the rule of clerics.

While Ahmadinejad was formally invited by Lebanese President Michel Suleiman and was to meet on Thursday with the head of the pro-Western bloc in the government - Prime Minister Saad Hariri - the splashiest welcome came from Hezbollah, Iran's stalwart ally.

Ahmadinejad's first state visit is a bold demonstration by Shiite-dominated Iran that it is undeterred by U.S. attempts to isolate it and roll back the clout Tehran has built up around the Middle East through its alliances with militant groups like Hezbollah and its accelerating nuclear program.

The first visit by an Iranian president in seven years, it also underlines the eroding position of the West's allies in the deeply divided country. A fragile unity government that combines a Western-backed coalition with Hezbollah and its allies is in power, but many fear it could soon collapse because of their rivalries.

While he was greeted with joy by many Shiites, Ahmadinejad's dramatic arrival only exacerbated fears among many Lebanese - particularly Sunnis and
Christians - that Iran and Hezbollah are seeking to impose their will on the country and possibly pull Lebanon into a conflict with Israel.

Standing alongside Suleiman at a news conference, the Iranian leader sought to depict his country as an ally of the entire nation, not just the Shiite Hezbollah movement.

"We seek a unified, modern Lebanon, and we will stand with the people and government of Lebanon - and with all elements in the Lebanese nation - until they achieve all their goals," Ahmadinejad said, adding that both countries oppose Israeli aggression.

"We completely support the Lebanese people's fight against the Zionist enemy," he said.

Hezbollah boasts widespread support among Shiites, virtually runs a state-within-a-state in Shiite areas and its guerrillas are Lebanon's strongest armed force. Iran, whose ties to the group date back nearly 30 years, funds Hezbollah to the tune of millions of dollars a year and is believed the supply much of its arsenal.

Iran also helped rebuild homes in southern Lebanon's Shiite heartland after the widespread destruction caused in Hezbollah's 2006 war with Israel.

For Ahmadinejad's arrival, thousands of Lebanese - mainly Hezbollah supporters - lined the highway from the airport into Beirut, waving Lebanese and Iranian flags while loudspeakers blasted anthems and women in the crowd sold Hezbollah flags and balloons to onlookers.

Trailed by heavily armed security in bulletproof vests, Ahmadinejad smiled and waved to the crowds from the sunroof of his black SUV as he headed from the airport to the presidential palace to meet Suleiman.

"Ahmadinejad has done a lot for Lebanon, we are here to thank him," said Fatima Mazeh, an 18-year-old engineering student who took the day off from classes to join the crowds. "He's not controlling Lebanon. Everyone has a mind and can think for himself. We are here to stand with him during the hardest times."

Ali Chehade, a 32-year-old math teacher, told his kids to take the day off for the visit.

"Ahmadinejad is a big leader in the region because of his words about the resistance," he said, referring to Iran's support for what Hezbollah touts as its armed resistance to Israel.