WASHINGTON — President Barack Obama said Friday he is releasing an additional $70 million in military aid for Israel, a previously announced move that appeared timed to upstage Republican rival Mitt Romney’s trip to Israel this weekend.

The stepped-up US aid, first announced in May, will go to help Israel expand production of a short-range rocket defense system. The system, known as Iron Dome, has proved successful at stopping rocket attacks fired at Israeli civilians from close range, including from Gaza.

The new law would also enable Israel to upgrade air refueling capabilities, missile defense capabilities and specialized munitions. The law also seeks to enhance cooperation on preventing arms smuggling from the Sinai to Gaza and offer the IAF additional training and exercise opportunities in the United States to compensate for Israel’s limited air space.

Defense Minister Ehud Barak praised the Obama administration’s decision and said it represented “consistent support” for Israel on the part of the White House and the US Congress.

“The new law, along with the $70 million in additional funding for Iron Dome, are another expression of the consistent support of the Obama administration and also Congress for the security of Israel,” Barak said. “We are thankful and welcome [the support],” he added.

Obama announced the new military assistance as he signed a bill in the Oval Office expanding military and civilian cooperation with Israel.

As he sought to underscore his commitment to Israel, the president first said the increased aid totaled $70 million, then said the number was actually $70 billion, even though the smaller figure is correct.

Obama said the bill underscores the United States’ “unshakable commitment to Israel.”

The White House focus on Israel this week comes as Romney prepares to visit Jerusalem. The presumptive GOP nominee is a critic of Obama’s policy toward Israel and has promised to ramp up US aid to the Jewish state, although Obama officials say the administration already provides record levels of funding.

A Romney spokeswoman said the former Massachusetts governor was happy to see steps being taken to enhance security cooperation with Israel.

“Unfortunately this bill does nothing to address yesterday’s evasiveness from the White House on whether President Obama recognizes Jerusalem as the capital of Israel, which raised doubt about the president’s commitment to our closest ally in the region,” said Romney spokeswoman Amanda Henneberg.

“The Enhanced Security Cooperation Act sends an unequivocal message of support to the people of Israel at a time of great uncertainty throughout the entire Middle East, and reminds the region of the unbreakable bond between our two nations,” said Israel’s Ambassador to Washington Michael Oren.

Also on Friday, the Pentagon and Lockheed Martin Corp. reached an agreement to integrate Israeli systems into the American company’s F-35 fighter jet.

The $450 million program will enhance electronic warfare equipment on the jets, according to sources familiar with the negotiations, Reuters reported.

The deal, to be finalized in coming weeks, marks a big step forward for Israel’s $2.75 billion agreement, signed in 2010, to buy 19 F-35 jets; it includes options for up to 75 of the radar-evading fighters, according to Reuters.

The agreement will allow increased participation in the F-35 Joint Strike Fighter program by Israeli companies, including Elbit Systems Ltd. and Israel Aerospace Industries, which will start building wings for the radar-evading warplane, Reuters reported.