By James Reynolds BBC Jerusalem Correspondent

The accepted international solution to the Israeli-Palestinian conflict appears to be very clear - two states side by side. But the Palestinians are now questioning this.

They say that continued Israeli settlement expansion and road building inside the West Bank may kill off the possibility of a viable Palestinian state.

The danger here is that the Israelis have become so successful in changing the demographics and the geography on the ground that anything left to the Palestinians won't be viable

Michael Tarazi PLO legal advisor

They accuse Israel of trying to join the dots between settlements, of trying to encircle and cut off Palestinian towns.

Palestinian Liberation Organisation legal advisor Michael Tarazi believes that new Israeli outposts, settlements and roads in the West Bank may have a fatal effect on the possibility of a two state solution.

"The danger here is that the Israelis have become so successful in changing the demographics and the geography on the ground that anything left to the Palestinians won't be viable," he says.

"The idea of two states is now being seriously reconsidered by the Palestinians because we don't want a state that's simply a glorified Indian reservation."

Terje Larsen, the UN special co-ordinator here, echoes some of these views.

"We in the UN share these concerns about settlements and roads which will make it difficult if not impossible to establish a viable, contiguous state."

But Israeli officials reject the assertion that settlements are expanding to the point of threatening a future Palestinian state.

Join the dots

"The demographics over the past two years have hardly changed in the West Bank and the Gaza Strip," says Mark Sofer, a senior official from the Israeli Foreign Ministry.

"I really take issue with the assertion that it is the settlement issue which is preventing a solution to the Israeli Palestinian conflict.

"Just two years ago we had a solution on the table proposed by the United States, endorsed by the international community, which called for this two state solution and exchanges of territory in that respect. And the Palestinians walked away from it."

There's one group of settlements in particular that the Palestinians have highlighted - the Binyamin bloc outside the Palestinian town of Ramallah.

The Palestinians say the Israelis are attempting to isolate Ramallah from the rest of the West Bank.

To check this, I went to see the Mayor of the Binyamin Bloc, Pinhas Valerstein. I showed him a map prepared by the Palestinians - outlining the projected expansion of his settlements.

"No, it's much bigger, for sure," the Mayor told me, pointing to the expansion area the Palestinians had drawn. He believes that the Palestinians have actually underestimated his ambitions.

His plans to encircle and cut off Ramallah go much further than the Palestinians have predicted.

Pinhas Valerstein is one of many settlers who believe that there should not be a Palestinian state in the West Bank.

He's doing his best to make sure that his settlements expand and cut off Palestinian areas.

Claimed freeze

A government freeze on new settlements appears to make very little difference to his plans. He simply goes ahead and starts new buildings anyway.

"Does the government try to stop you or not?" I asked him.

"They cannot stop me. No-one can stop you in your land if you have a plan."

Jewish settlements

There are 145 settlements in the West Bank and Gaza Strip 400,000 people live in settlements, including 11 settlers quarters in East Jerusalem Almost 40,000 houses have been built in settlements since the signing of the Oslo peace accords in 1993 Source: Peace Now

Many here believe the Israeli Prime Minister Ariel Sharon is with the settlers - despite his government's claimed settlement freeze.

Since Mr Sharon came to power a year and a half ago, left wing groups say that settlers have started up dozens of outposts - or makeshift settlements - in the West Bank. They say that only a tiny fraction have been dismantled.

Many observers find it hard to reconcile Mr Sharon's support for the settler movement with his publicly stated belief that there should, in the end, be a Palestinian state. Many believe he can't have it both ways.

According to the leading Israeli left wing politician Yossi Beilin, Mr Sharon's vision of a Palestinian state is "a joke rather than a state".

Binational state

The Palestinians believe that Mr Sharon is helping the settlers to prevent the creation of a meaningful Palestinian state.

PLO legal advisor Michael Tarazi says that because of this, the Palestinians are now having to consider abandoning support for a two state solution.

Palestinians burn a model of a Jewish settlement

The alternative, for them, is a one-state-for-all plan - a single binational country encompassing Israel, the West Bank and Gaza.

"Our ultimate strategy will be based on whether or not the international community decides to intervene," he says.

"Whether or not responsible Israelis get a hold of their senses and actually stop what their government's doing.

"But if that doesn't happen we certainly will be forced to consider re-evaluating our position and moving from a movement of equal nationhood to equal citizenship."

That's something that Israel would not accept. A single state would, within a few years, have an Arab majority - destroying for Israelis the concept of a Jewish state.

Israeli officials believe the Palestinians are trying to find a pretext with the settlement issue to avoid having to consider a two state solution.

"I cannot exacerbate enough the fear in Israeli society that the Palestinians are finding every excuse under the sun to walk away from the table - as they did two years ago," says Mark Sofer.

But as Israel continues to expand its presence in the West Bank, Palestinians see the land they hope will make up their state shrinking and the possibility of a two state solution receding.