Why Hamas chose to attack Israel now, after decades of conflict

• Hamas launched its deadliest-ever attack on Israel over the weekend.
• Militants entered Israel using paragliders and through security fences, killing and capturing civilians.
• Analysts say the terror group was trying to exploit regional instability.

As Israel reels from the worst terror attack in its history, focus is turning to the timing of the invasion by militant group Hamas.

The attacks started early Saturday, when militants used paragliders and broke through security fences on Israel's border with Gaza, killing more than 700 people and taking hundreds of civilians and military personnel captive.

US officials told NBC News the attacks were likely a bid to derail high-stakes negotiations, backed by the US, that were underway to normalize Israel's relations with Saudi Arabia.

Saudi Arabia has historically refused to recognize Israel's legitimacy, and hostilities between the states date back to the 1948 Arab-Israeli war.

But Saudi Arabia's ruler, Mohammed bin Salman, is keen to exploit the economic benefits of potentially normalizing ties with Israel, and there were hopes that other Arab states would follow suit.

Iran, Hamas' main backer, has long opposed attempts to normalize relations between Israel and its regional neighbors.

The Financial Times reported on Sunday that US officials were trying to establish if there was any involvement in the Israel attacks by Iran, with conflicting reports emerging over the weekend on whether Iran was involved.

The success of Israeli-Saudi talks now appears to be remote, with the concessions Riyadh requested in how Israel treats Palestinians even less likely to be agreed on in the wake of the attack, and Israel's declaration of war on Hamas.

Hamas itself has said the attacks were a response to Israeli settlers entering the al-Aqsa mosque in Jerusalem, the third holiest site in Islam and a long-standing flash point.

But a Hamas official also told Reuters that the operation had been years in the making, meaning the group is likely seeking to exploit Muslim grievance over recent events at the site and the wider diplomatic situation is the real motive for the attack.

"The reality is that while Hamas has dressed up the attack as a response to Israeli incursions around the al-Aqsa mosque in Jerusalem, it chose to trigger this conflict - at this time and in the way it did - as a way to impose itself in that wider diplomacy," wrote The Guardian's Middle East correspondent Peter Beaumont.

Another factor likely behind the timing of the attack is recent political turmoil in Israel, say analysts.

Israel's Prime Minister Benjamin Netanyahu has been seeking to curtail the authority of Israel's Supreme Court in the wake of probes into corruption allegations against him, sparking mass protests.

"There is a sense among Israel's adversaries that it "has never been more divided, never been weaker, never been more torn apart," James Stavridis, a former commander of NATO, told NBC News.