There are questions that rarely get asked in Washington. For years, the mantra that America's intimate alliance with Israel was as good for the US as it was the Jewish state went largely unchallenged by politicians aware of the cost of anything but unwavering support.
But swirling in the background when Binyamin Netanyahu, the Israeli prime minister, arrives in Washington tomorrow to patch up relations with the White House will be a question rarely voiced until recently: is Israel ‑ or, at the very least, its current government ‑ endangering US security and American troops?
Netanyahu would prefer to be seen as an indispensable ally in confronting Islamist terror. But his insistence on building Jewish settlements in East Jerusalem, which is causing a deep rift with Washington, is seen as evidence of a lack of serious interest in the establishment of a viable Palestinian state. That in turn is seen as fueling hostility towards the US in other parts of the Middle East and beyond, because America is perceived as Israel's shield.
In recent months Barack Obama has said that resolving the Israeli-Palestinian conflict was a "vital national security interest of the United States". His vice-president, Joe Biden, has confronted Netanyahu in private and told the Israeli leader that Israel's policies are endangering US troops in Iraq and Afghanistan. Senior figures in the American military, including General David Petraeus who has commanded US forces in both wars, have identified Israel's continued occupation of Palestinian land as an obstacle to resolving those conflicts.
More recently, Israel's assault on ships attempting to break the Gaza blockade has compromised relations with Turkey, an important American strategic ally.
A former director of intelligence assessment for the US defence secretary, last month caused waves with a paper called Israel as a Strategic Liability? In it, Anthony Cordesman, who has written extensively on the Middle East, noted a shift in thinking at the White House, the US state department and, perhaps crucially, the Pentagon over the impact of Washington's long-unquestioning support for Israeli policies even those that have undermined the prospects for peace with the Palestinians.
He wrote that the US will not abandon Israel because it has a moral commitment to ensure the continued survival of the Jewish state. "At the same time, the depth of America's moral commitment does not justify or excuse actions by an Israeli government that unnecessarily make Israel a strategic liability when it should remain an asset. It does not mean that the United States should extend support to an Israeli government when that government fails to credibly pursue peace with its neighbors.
"It is time Israel realized that it has obligations to the United States, as well as the United States to Israel, and that it become far more careful about the extent to which it test the limits of US patience and exploits the support of American Jews."
Cordesman told the Guardian that the Netanyahu government has maintained a "pattern of conduct" that has pushed the balance toward Israel being more of a liability than an asset.
"This Israeli government pushed the margin too far," he said. "Gaza was one case in point, the issue of construction in Jerusalem, the lack of willingness to react in ways that serve Israel's interests as well as ours in moving forward to at least pursue a peace process more actively."
It was a point made forcefully by Biden to Netanyahu in March after the Israelis humiliated the American during a visit to Jerusalem by announcing the construction of 1,600 more Jewish homes in the city's occupied east.
The Israeli newspaper Yedioth Ahronoth reported that at a meeting between the two men, Biden angrily accused Israel's prime minister of jeopardizing US soldiers by continuing to tighten the Jewish state's grip on Jerusalem.
"This is starting to get dangerous for us. What you're doing here undermines the security of our troops who are fighting in Iraq, Afghanistan and Pakistan. That endangers us and it endangers regional peace," Biden told Netanyahu.
Obama's chief political adviser, David Axelrod, said the settlement construction plans "seemed calculated to undermine" efforts to get fresh peace talks off the ground and that "it is important for our own security that we move forward and resolve this very difficult issue".
Netanyahu sought to head off the issue when he spoke to pro-Israeli lobbyists in Washington earlier this year. "For decades, Israel served as a bulwark against Soviet expansionism. Today it is helping America stem the tide of militant Islam. Israel shares with America everything we know about fighting a new kind of enemy," he said. "We share intelligence. We co-operate in countless other ways that I am not at liberty to divulge. This co-operation is important for Israel and is helping save American lives."
But that argument is less persuasive to the Americans now. Last month, Israel's ambassador to the US, Michael Oren, said the Jewish state had suffered a "tectonic rift" with America. "There is no crisis in Israel-US relations because in a crisis there are ups and downs," he told Israeli diplomats in Jerusalem. "Relations are in the state of a tectonic rift in which continents are drifting apart."
Oren said that assessments of Israeli policy at the White House have moved away from the historic and ideological underpinnings of earlier administrations in favour of a cold calculation.
Cordesman said it is too early to tell whether Netanyahu has fully grasped that while there will be no change in the fundamental security guarantees the US gives Israel, "the days of the blank cheque are over".
He added: "I think it is clear there is more thought on how to deal with Gaza, how to deal with the underlying humanitarian issues, less creating kinds of pressures which frankly, from the viewpoint of an outside observer, have tended to push Hamas not toward an accommodation but toward a harder line while creating of all things an extremist challenge to Hamas. But until you see the end result, some comments and some token actions don't tell you there's been a significant shift."