ERUSALEM, Nov 22 (Crispian Balmer/Reuters) - Israel is growing increasingly concerned that its relationship with the United States, a defining feature of Middle East diplomacy for half a century, no longer has the core strategic value for Washington it once had.

No matter how many times U.S. officials, from President Barack Obama down, send reassuring messages that they are deeply committed to Israeli security, Jewish leaders fret that Washington now sees Israel as more of a hindrance than a help.

There is definitely a new American perception that does not see Israel as a strategic asset in the Middle East, said Reuven Rivlin, speaker of the Israeli parliament.

This is a development that even we, the veteran politicians, see as something new, he said in an interview with the Jerusalem Post at the weekend.

Relations between the two countries have certainly recovered from a low point in March, when a row over West Bank settlement building earned Israeli Prime Minister Benjamin Netanyahu a rare dressing down by U.S. Secretary of State Hillary Clinton.

But the alarm bells are ringing again in Israel, following days of uncertainty over a package of incentives drawn up by Washington to persuade Netanyahu to impose a temporary building freeze and revive stalled peace talks with the Palestinians.

Netanyahu announced the U.S. offer as a done deal more than a week ago, but his efforts to get written promises have proved excruciatingly difficult, raising questions in Israel about the sincerity of the offer and what strings were attached.

REWARDING BAD BEHAVIOR

The Palestinians scoff at the idea that the United States might be losing its ardour for Israel, saying the U.S. promise of inducements, including $3 billion worth of fighter jets, is evidence of the Jewish state's privileged status in Washington.

The enticements have also raised eyebrows in the United States, with analysts doubting the wisdom of offering Israel incentives to get it to introduce a temporary halt to settlement building that is deemed to be illegal by the World Court.

For the first time in memory, the United States is poised to reward Israel for its bad behavior, Daniel Kurtzer, a former U.S. Ambassador to Israel, wrote in Sunday's Washington Post.

Kurtzer added that Netanyahu had made a major mistake by including military aid on the list of bribes.

He has made those needs contingent, negotiable, optional. Israel's security requirements are now merely a bargaining chip with which to negotiate what Jerusalem will or will not do to advance the peace process, he said.

U.S. military aid is traditionally ringfenced, well apart from peace negotiations. In the same vein, analysts said an apparent promise by Clinton to provide Israel diplomatic protection in the United Nations was normally a fact of life, not part of any political horse-trading between the two allies.

Before we can even get to grips with the complexities of dealing with the Palestinians, we find ourselves head-to-head with Washington, the Jerusalem Post said in a Nov. 19 editorial. Didn't we used to be on the same side?

Some Israeli officials think Obama is responsible for the increasingly complex relations, and look back with nostalgia at the extremely close rapport between previous U.S. and Israeli leaders, such as Bill Clinton and Yitzhak Rabin.

Opposition Israeli politicians pin the blame on Netanyahu, a tough right-winger, who clearly feels more comfortable with the U.S. Republican party than with the Democrat Obama.

You have turned Israel into a weak, frightened, insular, self-conflicted country, which is losing its only friend in the world, Tzipi Livni, head of the opposition Kadima party, told Netanyahu in a recent parliamentary debate.

MILITARY WORRIES

At a deeper level, the on-going sense of uncertainty in Israeli circles is fuelled by evolving U.S. military objectives.

General David Petraeus, commander of U.S. and NATO forces in Afghanistan, launched a debate in March when he said that Israeli-Palestinian tensions had had an enormous impact in the Muslim world where his troops were based.

Petraeus said the Middle East peace process had to keep moving forward to help the U.S. military position -- an assertion quickly challenged by Israeli rightists who denied any such linkage.

His stance explains why Obama has put enormous emphasis on restarting the stalled peace talks despite obvious pessimism on both the Palestinian and Israeli side, not to mention at home.

An Israeli official, who declined to be named because of the sensitivity of the issue, said Netanyahu wanted to bring Iran into the Middle East equation, proffering concessions in return for a promise of U.S. action against Tehran's nuclear project.

But his attempts appear to have failed, with U.S. Defense Secretary Robert Gates this month publicly disagreeing with his assertion that only a credible military threat would halt Iran.

While such open discord might be unusual in the Israeli-U.S. couple, no-one expects it to end in divorce.

We have had our ups and downs, but our friendship is so deep it easily overcomes such problems, said an Israeli cabinet minister.