The United States has signed a record $38bn deal to provide Israel with military assistance over a 10-year period - the largest such agreement ever by the US with any country.

Following 10 months of frequently tense negotiations, the two allies finalised the memorandum of understanding (MOU) with a signing ceremony on Wednesday in Washington DC.

"Both Prime Minister [Benjamin] Netanyahu and I are confident that the new MOU will make a significant contribution to Israel's security in what remains a dangerous neighbourhood," US President Barack Obama said in a statement, according to Reuters news agency.  

Under the terms, Israel will receive $3.8bn a year from the US - up from the $3.1bn Washington currently gives Israel annually under a 10-year deal that ends in 2018.

The agreement was described as the "single largest pledge of bilateral military assistance in US history", but it also involves major concessions by the Israeli government, which will no longer be able to seek additional annual funds from the US Congress over and above the new package.

Al Jazeera's Patty Culhane, reporting from Washington DC, said the annual $3.8bn figure did not mark a big change "compared with what Israel was getting in 2015 or 2016".

"It sounds like a bit of a difference, but then if you look at the money that the US Congress routinely gives Israel on top of that $3.1bn, it's really not that much more," Culhane said.

"In 2015, the US Congress gave Israel $620m for missile defence, so basically Israel is going to get the same amount as it's been getting."

The figure also is significantly lower compared with the $4.5bn - $5bn sums that Netanyahu said he was seeking when he first entered the negotiations, according to Culhane.

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Marwan Bishara, Al Jazeera's senior political analyst, said Obama had to answer why the US signed now a record military assistance deal with Israel.

"Why is the American military aid increasing, and not decreasing?" Bishara said, citing Israel's peace agreements with neighbours such as Egypt and Jordan, as well as Iran's recent nuclear deal.

"Whenever the situation improves for Israel, American aid increases. And what happens? The Israeli policy becomes more and more radicalised. Today, and for the last 40 years, Israel has become ever more radical. The more aid it got, the more radical Israel has become.

"That's the question for President Obama to answer."

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Efraim Inbar, a professor at Israel's Bar-Ilan university, told Al Jazeera from Jerusalem that Israel needed the agreement to upgrade ageing weapons systems, including aircraft and missile batteries.

"And there are many more threats looming over the horizon: Iran may become nuclear, the Islamic State is still there, there is a possibility of an escalation over the Golan Heights border," he said, referring to the Islamic State of Iraq and the Levant (ISIL, also known as ISIS). 

Under the deal, Israel's ability to spend part of the US funds on Israeli military products will be gradually phased out, eventually requiring all of the funds to be spent on American military industries, according to the Associated Press news agency.

Israel's preference for spending some of the US funds domestically had been a major sticking point in the deal.

The new US-Israel agreement also includes, for the first time, $5bn funding for missile defence programmes. Under the previous arrangement, Congress approved funds for missile defence separately and on an annual basis.

The deal was reached despite mounting frustration within the Obama administration at Israel's policy of building settler homes on occupied Palestinian territory.

Washington has warned that Netanyahu's policies are putting at risk hopes of an eventual peace deal.

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Source: Al Jazeera News And Agencies