* Netanyahu fears Islamic ambush at conference
* Sends a deputy in his place to Washington
* Republicans say Obama is snubbing Israel
(Adds background, Netanyahu quotes)
By Douglas Hamilton and Dan Williams
JERUSALEM, April 9 (Reuters) - Israeli Prime Minister Benjamin Netanyahu has cancelled a planned trip to Washington next week for President Barack Obama's 47-country nuclear security conference.
He made the decision after learning Egypt and Turkey intended to raise the issue of Israel's assumed atomic arsenal at the meeting, a senior government official said on Friday.
Israel is believed to be the only nuclear-armed power in the Middle East, but has never confirmed or denied it. It has not signed the nuclear Non-Proliferation Treaty (NPT).
Netanyahu saw Obama at the White House late last month to discuss the stalled Israeli-Palestinian peace process. But they failed to see eye to eye and bilateral ties remain strained.
"The prime minister has decided to cancel his trip to Washington to attend the nuclear conference next week, after learning that some countries including Egypt and Turkey plan to say Israel must sign the NPT," the official said.
Deputy Israeli Prime Minister Dan Meridor will stand in for Netanyahu at the Nuclear Security Summit (NSS) on April 12-13.
Netanyahu's attendance would have been the first by an Israeli premier at an international nuclear forum. Aides said he originally agreed to go after being reassured by the United States that the NSS communique would focus on efforts to secure fissile material with no allusions to Israel's undeclared arms.
The NSS had also offered Netanyahu an opportunity to drum up support for sanctions against arch-foe Iran, which the West suspects of seeking nuclear weapons despite denials from Tehran. Neither Iran nor North Korea will attend the NSS.
"This conference is about nuclear terrorism," Netanyahu told reporters on Wednesday. "And I'm not concerned that anyone will think that Israel is a terrorist regime. Everybody knows a terrorist and rogue regime when they see one, and believe me they see quite a few -- around Israel."
Based on estimates of the plutonium production capacity of its Dimona reactor, Israel may have stockpiled 80 to 200 nuclear warheads since the late 1960s, independent experts say.
Israeli leaders do not comment on this capability under an "ambiguity" policy billed as warding off enemies while avoiding the kind of provocations that can trigger regional arms races.
The official reticence, and its tacit acceptance by the United States, has long aggrieved Arab and Muslim powers.
Like India and Pakistan -- both also slated to attend the NSS -- Israel is outside the NPT and thus avoids mandatory international inspections of its nuclear facilities. Unlike them, it has not openly tested or deployed atomic weapons.
Netanyahu had been expected to arrive late to the NSS due to Monday's Holocaust memorial ceremonies in Israel, and to spend an additional day in Washington after the summit's conclusion.
The White House had said Obama would not hold a separate working meeting with Netanyahu, given their recent talks. On Thursday, Netanyahu's office had said he might cut short his Washington trip to allow for a stop in New York en route home. News of Netanyahu's withdrawal from the NSS was noted by U.S. Republicans, who saw a snub by the Obama administration.
"Israel is our strongest ally in the Middle East and one of our strongest allies anywhere around this globe," Liz Cheney, daughter of former Vice President Dick Cheney, told the Southern Republican Leadership Conference in New Orleans.
"And President Obama is playing a reckless game of continuing down the path of diminishing America's ties to Israel." (Additional reporting by Joseph Nasr in Jerusalem and Steve Holland in New Orleans; editing by Andrew Roche)