When a king and a U.S. senator cruise the Dead Sea shoreline on big bikes, these would-be easy riders need yield to no one. But as King Abdullah of Jordan and Sen. John Kerry of the Senate Foreign Relations Committee roared through the desert landscape last weekend on a break from the World Economic Forum, the question hanging in the air like the bitter haze above the salt sea was all about green lights and red lights on the road to Middle East peace.

The king is looking for a sign from President Barack Obama. It could come after the president's meeting with Israeli Prime Minister Benjamin Netanyahu on Monday, or it could come tomorrow, or maybe even as late as the first week of June, when Obama will make what's already being billed as a historic speech to the Muslim world. But the sought-after signal is quite specific: a clear, forceful American commitment aimed at ending expansion of Israeli settlements in the occupied Palestinian territories. That would mean a freeze, full stop. There would be no acceptance of so-called "natural growth" of existing settlements, no place for illegal but tacitly tolerated new ones, no patience with efforts to remake the map on the ground.

That red light for Netanyahu will be taken as a green light for Arabs, say senior Jordanian officials who did not want to be named because of the obvious sensitivity of the diplomacy. It would be seen as the signal that this U.S. administration, unlike so many before it, is willing to move beyond platitudes about bringing the parties together and begin to play a role that would be as active, tough and direct in the Middle East as Washington played in the Balkans a decade ago.

Upon seeing that signal, Arab advocates of peace are supposed to be ready to shift into high gear. And Abdullah, if not precisely the leader of the pack, has assumed the role of trying to keep it headed in the right direction. According to the same sources, plans call for Israel-Palestine, Israel-Lebanon and Israel-Syria working groups to be negotiating in earnest in Washington by the middle of this summer.

It's a good guess Abdullah will get that signal he wants and needs. Vice President Joe Biden bluntly told the powerful American Israel Public Affairs Committee (AIPAC) at its convention earlier this month that "Israel has to work toward a two-state solution"—a proposition Netanyahu has been trying to back away from. "You're not going to like my saying this," Biden told the crowd, but that would mean Israel would "not build more settlements, [would] dismantle existing outposts," and would allow the Palestinians freedom of movement. "This is a 'show me' deal—not based on faith," said Biden. "Show me." Kerry, now in Biden's old chairmanship at Senate Foreign Relations, carried a similar message to the Dead Sea conference.

But the Arabs, in fact, are not in a good position to respond the way the White House would like them to. Some in Washington have described Abdullah as "the whip" of the Arab and Muslim peace camp. The term is used in Congress to describe a political party's chief enforcer. But it originally applied to the huntsman who keeps a pack of hounds on the right scent. Abdullah's job is actually more like herding cats.