JERUSALEM  Iran seems to be hurtling toward nuclear weapons capacity, Hezbollah could win Sunday’s election in Lebanon and Hamas is smuggling long-range rockets into Gaza again. So why is President Obama focusing such attention on the building of homes by Israeli Jews in the West Bank?

That, in essence, is the question being angrily posed by the Israeli government of Prime Minister Benjamin Netanyahu and underscores one of the biggest shifts in American policy toward the Israeli-Palestinian conflict in three decades. While every administration has objected to Israeli settlement building in occupied lands, the Obama administration has selected it as the opening issue that could begin to untie the Gordian knot of the conflict.

American officials hope that by getting Israel to freeze settlement building on land where the Palestinians expect to build their future state, they can then press Saudi Arabia and other regional powers to offer Israel concessions like low-level trade or tourism. In addition, stopping the construction would remove a major concern of the Palestinians that their land is slowly disappearing under settler housing. In his Cairo speech on Thursday, the president again called for an end to the settlement building.

“Obama may have found the soft underbelly of Israel, because ending settlements is a consensus issue in the world, among American Jewry and even among a majority of Israelis,” said Yossi Beilin, a former leftist minister and member of Parliament who now runs a private consulting firm. “He needs a strong regional coalition to leave Iraq  and not to leave it to Iran. And it seems like he sees ending settlements as a way to start this process. The only question is whether Netanyahu can do what is needed.”