Mitt Romney travels to Israel Sunday in hopes of proving to voters back home that, as president, he would strengthen ties with America's strongest ally in the Middle East.

Romney clearly sees an opening against Obama on Israel: Obama's support among traditionally Democratic Jewish supporters has weakened since 2008 and his relationship with Israeli Prime Minister Benjamin Netanyahu is widely seen as strained, while Romney and Netanyahu have a relationship that predates their politics.

"Prime Minister Netanyahu and Gov. Romney have a long-standing friendship that goes back 40 years," said Romney spokesman Ryan Williams, noting that both men worked for Boston Consulting Group in the 1970s.

Vying for Jewish-American voters and Americans living in Israel, Romney has accused Obama of "lecturing" and "undermining" Israeli leaders and says the president has effectively distanced the U.S. from its closest ally in the Middle East.

The Republican presidential contender argues that Obama hasn't been tough enough against Iran and chastised Obama for suggesting that Israel withdraw to its pre-1964 borders to encourage the Palestinians to restart negotiations over a Middle East peace pact.

Netanyahu at the time called Obama's position on Palestine "indefensible" -- a criticism that Romney repeated to an Israeli newspaper prior to his trip.

"Acting as a negotiator and usurping the primary role played by Israel in negotiating for its own future is not the right course for America to take," Romney told Israel Hayom, one of Israel's largest newspapers, which is owned by Las Vegas casino magnate Sheldon Adelson, a top contributor to Republicans, including Romney.

Romney has tough talk for Obama back home, but while in Israel on Sunday he plans to tone down his criticism so as not to be caught bashing the U.S. on foreign soil, aides said.

Romney's full day of events starts with a briefing from U.S. ambassador to Israel Dan Shapiro and meetings with Netanyahu, Israeli President Shimon Peres and others. He's planning a $60,000-a-plate fundraiser and later will deliver a speech on U.S.-Israeli relations. Aides say the speech won't contain any policy prescriptions.

Romney will say "that challenges and threats to Israel are in many ways challenges and threats to the U.S., [but that] Israel has the added burden of living in a much more dangerous neighborhood," said one adviser traveling with Romney. He will make the case that the U.S. "needs to do that much more to lock arms with Israeli leaders and convey to the world that we will treat threats to Israel as threats to America."

Back at the White House, Obama has been shadowing Romney's travels with his own headline-grabbing policy announcements, meetings with foreign officials and news of diplomatic trips.

Just before Romney arrived in Israel, Obama announced that he was signing a security pact that provides Israel with $70 million in defense assistance and he dispatched Defense Secretary Leon Panetta to Israel to determine what other U.S. assistance it needs.

"I have made it a top priority for my administration to deepen cooperation with Israel across the whole spectrum of security issues -- intelligence, military, technology," Obama said. "What this legislation does is bring together all the outstanding cooperation that we have seen, really, at an unprecedented level between our two countries that underscores our unshakable commitment to Israel security."