JERUSALEM (AFP) - Israel Prime Minister Benjamin Netanyahu has told United States Secretary of State John Kerry that he wants to annex a fourth bloc of West Bank settlements, army radio reported on Sunday.

Until now, Israel has always spoken of its intention to annex three blocs of settlements in any future agreement with the Palestinians: the Etzion bloc in the south; Maaleh Adumim to the east of Jerusalem; and the Ariel bloc in the north.

The report said Mr Netanyahu was proposing that Israel also keep hold of a group of settlements deep in the West Bank - Beit El, Ofra and Psagot - which lie to the north and east of Ramallah, the radio said.

A settlement bloc is an area where clusters of settlements have been established in relatively close proximity to one another, in which the majority of the West Bank's 367,000 settlers currently live.

If Israel was to keep hold of the "Beit El bloc" as well as the others, it would mean annexing a total of 13 percent of the occupied West Bank, the radio said, describing it as a "very large percentage" of the territory.

"In the negotiating room, Mr Netanyahu is talking about 13 per cent of territory," the radio's diplomatic correspondent Ilil Shahar said, quoting sources close to Netanyahu.

"Netanyahu is proposing to a (land) swap of three to four percent then paying for the rest," she said.

In previous rounds of negotiations, former prime minister Ehud Barak in 2001 spoke of Israel annexing six to eight percent, and in 2008, then premier Ehud Olmert spoke about 7 per cent.

The Palestinians want to keep Israel's annexation of land they want for a future state to an absolute minimum, and have spoken of a maximum land swap of about two percent.

Mr Netanyahu's office refused to comment on the report.

Mr Shaul Arieli, an expert on mapping and the future Israeli-Palestinian borders described the proposal as infeasible.

"If we're really talking about 13 per cent, we're talking about an idea that's a non-starter from the Palestinian point of view," he told the radio.

"Israel does not have the ability to compensate the Palestinians at that level, our potential for compensation is not more than 3 to 4 per cent, and of course the idea of paying is unacceptable."

Israel and the Palestinians embarked upon a nine-month track of direct negotiations at the urging of Mr John Kerry, at the end of July, which appear to have made little progress.

Currently, Mr Kerry's main focus is trying to get the sides to agree on a framework to guide the negotiations forward in the coming months.

Although the term "settlement block" has been used by Israeli leaders for years, the parameters of such areas have never been clearly defined, with the best indicator of their location being the looping route of the sprawling West Bank barrier.

The phrase is a euphemism for those settlements that are supposedly within the Israeli national "consensus" as being the areas that should and likely will remain part of Israel under any future peace agreement, according to settlement watchdog Peace Now.