By Matt Spetalnick
WASHINGTON (Reuters) - President Barack Obama signed a bill on Friday to strengthen U.S.-Israeli military ties as he sought to reassure American Jewish voters of his commitment to the two countries' close alliance on the eve of a visit to Israel by his Republican rival, Mitt Romney.
Obama used a White House ceremony to announce the United States would soon provide Israel with an additional $70 million in funding for its short-range rocket shield known as "Iron Dome," a project strongly backed by the powerful U.S. pro-Israel lobby.
His focus on strengthening cooperation with Israel appeared timed to upstage Romney, who has accused the president of undermining Washington's relationship with its number one partner in the Middle East.
Romney, whose Olympics-week visit to London has been plagued by diplomatic stumbles, will travel on Saturday to Israel, a stop his aides hope will resonate with Jewish voters at home.
He is expected to hold talks on Sunday with Israeli Prime Minister Benjamin Netanyahu, who has had a strained relationship with Obama.
As Obama signed the bill at his desk in the Oval Office, he said it underscored his administration's "unshakeable commitment" to Israel's security. Congress passed the legislation last week with broad support from Republicans and Obama's Democrats.
"I have made it a top priority for my administration to deepen cooperation with Israel across a whole spectrum of security issues," Obama said in the Oval Office.
He was flanked by U.S. Senator Barbara Boxer and Congressman Howard Berman, the bill's sponsors, and several prominent Jewish leaders, including Lee Rosenberg, chairman of AIPAC, the leading pro-Israel lobby, and Richard Stone, chairman of the Conference of Presidents of Major American Jewish Organizations.
Obama, criticized by some of Israel's U.S. supporters for being too tough on a close ally, wants to shore up his support among Jewish voters, who could prove critical in battleground states like Florida and Pennsylvania in the November 6 election.
OUTREACH TO ISRAEL'S SUPPORTERS
Obama received 78 percent of the Jewish vote in the 2008 election, but a nationwide Gallup poll in June showed him down to 64 percent backing versus Romney's 29 percent.
Obama angered many Israelis and their U.S. supporters last year when he insisted any negotiations on the borders of a future Palestinian state begin on the basis of lines that existed before Israel captured the West Bank and Gaza Strip in a 1967 war. His Middle East peace efforts have stalled.
Obama visited Israel as a candidate in the 2008 campaign but has not done so as president. He has insisted security ties with Israel have never been stronger, though he has pressed Netanyahu to hold off on any attack on Iran's nuclear sites to give diplomacy and sanctions more time to work.
Romney has accused Obama of being too hard on Israel and not tough enough with Iran.
The new bill calls for enhanced cooperation with Israel - the staunchest U.S. ally in the Middle East and a major beneficiary of military aid - on missile defense and intelligence, and increased access to advanced weapons.
Obama said Defense Secretary Leon Panetta would visit Israel soon to discuss further cooperation at a time of "heightened tensions in the region." Syrian President Bashar al-Assad is faces growing international pressure over his brutal crackdown against a 16-month-old uprising.
(Reporting By Matt Spetalnick; Editing by Vicki Allen)