President Barack Obama on Thursday articulated long-held but rarely-stated American support for a future Palestinian state within the armistice lines that have existed since the end of the Six Day War.

Israeli prime minister Benjamin Netanyahu, while visiting his ally in Washington the next day, rejected the forty year-old border situation as unrealistic. “We can’t go back to those indefensible lines,” he said.

The 1967 borders should be used as a basis for negotiations, said President Obama, “with mutually agreed swaps” of land.

Israeli settlement activity in the West Bank, which is home to some 300,000 Jewish colonists, has made it impossible for Israel to withdraw completely to within the old borders — which did not include East Jerusalem. 200,000 Israelis are estimated to live in that part of the ancient city which the Palestinians claim as their capital.

Agreed swaps would allow Israel to keep settlements in the West Bank in return for giving the Palestinians other land. Previous proposals, however, under which Israel would keep Jerusalem along with 6 percent of West Bank territory, home to 75 percent of the settler population, were rejected by the Palestinians. The Palestinian Authority’s recent inclusion of Hamas, which propagates the destruction of the Jewish state, doesn’t bode well for future negotiations.

The vast majority of West Bank settlers lives in what the Israelis refer to as “settlement blocs” which are actually entire towns, usually built close to the 1967 border. Up to 80,000, who live in small villages, would be forced to relocate unless far more generous land swaps than have ever been contemplated are agreed upon.

Isolated settlers tend also to be the more fanatic, however, making it difficult for the Israeli government to force them to leave their homes without risking political upheaval. When roughly 8,000 settlers had to abandon their livelihoods in Gaza in 2005, some wouldn’t leave until Israeli soldiers intervened. Now, the government even has an outspoken pro-settler party in its coalition whose leader and Israeli foreign minister Avigdor Lieberman prevented Netanyahu from extending a ten month settlement freeze last year.

Aside from the settler issue, the Israelis fear that a return to the 1967 borders would complicate their security — hence the prime minister’s use of the word “indefensible.” The occupation of the Palestinian territories, especially the land west of the Jordan River, provides Israel with a buffer while Israel’s military presence within the West Bank is aimed at preventing militants from launching rocket attacks and raids into Israeli territory. Major Israeli cities, including Tel Aviv, are situated mere miles from the West Bank’s western border, well within the range of missiles that Hamas previously fired from Gaza.

Although President Obama acknowledged in his address that “Israel must be able to defend itself, by itself, against any threat,” he also suggested a “full and phased withdrawal of Israeli military forces” from the Palestinian territories. As far as many Israelis are concerned, such a move would be impossible to reconcile with Israeli security.

The proposed “demilitarized” character of a tentative Palestinian state might convince the Israelis to give up their heavy security presence in the West Bank but they are unlikely to surrender all of their existing army bases that dot the territory, including facilities and patrols along the Jordan border.

During the most recent of direct negotiations, Prime Minister Netanyahu reportedly demanded Israeli troops both on Palestine’s side of the West Bank barrier and in the Jordan Valley — a proposal that both the Palestinians and the Jordanians rejected.