WASHINGTON — The Mideast foreign policy black hole has relentlessly sucked in American diplomacy for more than a half century and now awaits Barack Obama even as he refuses to show his hand before taking office.

While the Israeli assault on the Gaza Strip puts the perennial regional puzzle in stark relief for the incoming administration, it is just another in the long history of crises and bloody conflicts between the Jewish state and the Palestinians.

And there are signs that, despite the Gaza fighting, the Israel-Palestinian conflict may not — and should not — be the heart of U.S. policy in the Middle East after Obama takes office Jan. 20. Instead, analysts say, Obama may need to focus more on stemming the rise of Islamic extremism.

Conventional wisdom in the U.S. has long held that an Israeli-Palestinian peace would trigger a seismic shift in the region. Leaders across the Middle East would lose their excuse for refusing to accept the Jewish state as a legitimate neighbor. Thuggish Arab regimes could no longer use the conflict to rationalize their brutality and undemocratic behavior. Free elections would produce moderate, democratic rule.

That view, however, was seriously undercut with the rise to power of the militant Islamic group Hamas in Gaza, the impoverished Palestinian enclave separated by Israeli lands from the main Palestinian territory in the West Bank. Washington labels Hamas as a terrorist organization.

Hamas’ rise to authority in Gaza put the tiny slice of misery — a humanitarian sore abutted by Israel on two sides and bounded to the west by Egypt and the Mediterranean Sea — in the orbit of Iran, a non-Arab country with an extremist Islamic leadership that vows the destruction of Israel.

Hamas’ rise also buoyed another U.S. adversary, Syria, which has provided Hamas with funding and refuge to its leaders. Syria is an anomaly in the Arab world in that it is allied with the Iranians despite historic Arab-Persian animosity. Both Iran and Syria also offer essential support to Hezbollah, the Islamic movement that has accumulated power over large parts of Lebanon, on Israel’s north. Israel fought Hezbollah to a stalemate in Lebanon in August 2006.

Deeply afraid of growing Iranian influence in the region and fearing Tehran may soon be a nuclear power, Arab countries like Egypt, Jordan and Saudi Arabia — nominal but difficult U.S. allies — have been slow to add their voice and activities to the conflict in which the Israelis are pummeling Gaza with the aim of crippling Hamas.

The seeming ambivalence of such Arab states to act in face of the Israeli attacks, despite massive street protests in support of Hamas, has blunted a source of pressure on Israel to stop its deadly assault and signals a further evidence of wobbly Arab solidarity.

Even the Iranians and Syrians, apparently banking on changed U.S. policy under Obama, have been surprisingly restrained. The president-elect has promised to engage American foes diplomatically. Both Syria and Iran have much to gain and virtually nothing to lose by that engagement, which could be delayed or endangered if they get too out front over the Israel-Gaza conflict.

Thus some strategists now see the need for a fundamental shift in U.S. policy.

“You have to abjure the grand solution,” said Jonathan Adelman, professor of international studies at the University of Denver. All the new administration “can do is take a series of small steps.”

He argues that nongovernment players across the Middle East and southwest Asia are on the march, viewing themselves as on the winning side and will not be influenced to drop their radical Islamic agendas no matter what happens between Israel and Arab governments.

Hamas and Hezbollah as well as the Taliban in Afghanistan and al-Qaida chiefs holed up in the wilds of neighboring Pakistan are, to varying degrees, beyond the direct reach of diplomatic developments.

By comparison to that fight, “the cold war was easy,” Adelman contends. The groups “make the Soviet Communists look like warm and fuzzy characters.”

If that assessment is correct, as it would appear to be, Obama’s policy in the Middle East is deeply constrained because of the actors over which it holds no sway. That leaves the next administration confined to a rearguard action that seeks to contain the spread of militant and fundamentalist movements through small economic and security steps that allow the growth of alternatives — perhaps a broader Arab middle class able to enjoy the benefits of a slowly modernizing Middle East under competent governance.

While that does not discount the political and humanitarian imperative to solve the Israeli-Arab conflict, it does argue against expecting success in obliterating the regional black hole that has consumed so much U.S. diplomatic energy and dwindling resources.