Washington (CNN) Publicly the U.S. and Israel have been clashing over Iran's nuclear program, but quietly Israelis have been making another appeal: getting more U.S. funds for missile defense systems to defend against Iran's growing ballistic missile program.

A Republican congressional source told CNN that the Israelis are asking lawmakers to approve more than $300 million in additional U.S. funding for missile defense systems, above the $155 million the Pentagon is already requesting from Congress.

For the first time, the source said, Israel is asking the U.S. for procurement funding for the Arrow 3 missile, designed to counter longer-range Iranian ballistic missiles, and the David's Sling missile defense system, for shorter-range Iranian weapons.

There have been some spending request 'disconnects' in the U.S.-Israeli missile program because of the lack of communication between the two sides as a result of the controversy over the U.S. negotiations with Iran, some congressional sources have suggested.

Those talks center only on the nuclear weapons themselves. Iran's ballistic missile program would provide the delivery system for a nuclear weapon.

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It's not clear how the Pentagon will react to the Israeli proposal. But privately some are already noting that with the current U.S. defense budget crunch, it's likely something would have to be cut in the Pentagon budget to pay for the Israeli request. That seems unlikely to happen.

The funding request also comes as tensions between the Obama administration and Israeli government have boiled over. Prime Minister Benjamin Netanyahu on Tuesday gave a speech to Congress, held against White House wishes, objecting to the Iran deal.

That could complicate efforts by Israel to boost funding for the missile defense projects, which helps push aid to Israel to well over $3 billion per year. Or it might provide a way of patching up ties between the two countries if the deal Netanyahu opposes goes through.

National Security Adviser Susan Rice, in an address Monday to the major pro-Israel lobby AIPAC, emphasized continuing American support for missile-defense programs and other efforts to protect Israel's security.

"Last year, we provided Israel with the largest package of security assistance ever. And that's money very well spent," she said. "Because it goes directly to bolstering Israel's ability to defend itself, by itself, in a very tough neighborhood."

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She added, "We're maintaining Israel's qualitative military edge with new defense technologies and access to the most advanced military equipment in the world."

The Department of Defense declined to speak about the funding request, and Israeli officials didn't response to requests for comment.

U.S. intelligence officials have been warning for months that Iran continues to expand its long-range ballistic missile efforts, with the goal of being able to attack Israel and possibly achieving intercontinental targeting to attack Europe and the East Coast of the United States in the coming years.

According to a 2014 Air Force intelligence report, Iran for years "has placed significant emphasis on developing and fielding ballistic missiles to counter perceived threats from Israel and coalition forces in the Middle East and to project power in the region."

The report concluded that "Iran has a substantial inventory of missiles capable of reaching targets throughout the region, including Israel, and the regime continues to develop more sophisticated missiles."

James Clapper, director of national intelligence, last week told Congress that "the Iranians have continued on their space-launch vehicle program and recently put into orbit a satellite."

He continued, "Obviously, that -- any work they do on missiles could conceivably go towards work on an intercontinental ballistic missile."

But he noted, "It's going to be hard to determine whether a given missile is launched for the purposes of a space-launch vehicle, a satellite they want to put into space, because if they do that, they also acquire proficiency expertise and experience in what could be an ICBM."