Israeli intelligence believes that the political crisis engulfing Lebanon is more likely to be the result of Prime Minister Saad Hariri’s troubled relations with Saudi Arabia than Iranian interference in the country.

But both Mossad and the IDF have been warning for the past year that Hezbollah, the Shia militant group sponsored by Iran, has deepened its hold on Lebanon’s government and especially its armed forces. Footage supplied to Washington this year shows Hezbollah fighters in Syria using weapons supplied originally to the Lebanese army by the United States.

Mr Hariri caused widespread surprise when he resigned in a televised statement on November 4 from Riyadh, saying that he feared for his life. But Lebanon’s President Michel Aoun said he would not accept the resignation until Mr Hariri returned home to Lebanon — which he has yet to do.

In a stark message, Mr Aoun accused Saudi Arabia of detaining Lebanon’s prime minister in violation of human rights law.

Israeli Prime Minister Benjamin Netanyahu responded to the crisis in Lebanon by flagging up the role of Iran: “This is a wake-up call to the international community to take action against Iranian aggression,” he said in a statement after the resignation.

But in the days since, the view has developed that the key lies in Mr Hariri’s relations with the Saudis.

Israeli intelligence sources say that, while the Saudi leadership may have expected Mr Hariri to assert some control over Hezbollah, Israel has long regarded Lebanon as a failed state where Iran and its proxies hold sway.

The chief concern now is that the situation in Lebanon will be replicated in Syria, where planning for the aftermath of the civil war is well under way and Hezbollah and Shia deployments risk becoming permanent Iranian bases for missiles, radar and fighter-jets.

Prior to the civil war, President Bashar al-Assad did not allow operations against Israel from Syrian territory, ensuring that a ceasefire has held on the Golan Heights since 1973.

But Iran provided steadfast military and economic support to the Assad regime throughout the conflict and has since secured the rights to build an air and naval base on Syrian territory in return.

Israeli officials say a US-Russian agreement signed last week in Jordan on “de-escalation zones” in southern Syria does not provide clear assurances to Israel that Iranian forces will not operate close to its border. In any event, however, Iranian missile batteries and air-bases would still be capable of striking Israeli targets even if they were stationed deep within Syria.

“Israel will continue to operate in Syria, including in southern Syria, according to our understanding and our security needs,” Mr Netanyahu told the Knesset on Monday. “Iran knows that we will not agree to their entrenchment in Syria.”

The message was clear: Israel is not about to let Syria become another Lebanon.