It would be tough to find anybody in Congress, from either party, opposed to sending Israel more money for its Iron Dome air defense system, which has been instrumental in protecting the country from rockets fired by Hamas. But the additional $225 million Israel has requested for the anti-rocket system could be held up until September, as the parties spar over how Congress should distribute the money.

Senate appropriators have inserted the $225 million for the Iron Dome into their version of a $3.6 billion emergency supplemental spending bill that would primarily address the crisis of unaccompanied migrant children entering the United States from Central America.

But Republicans in both chambers are balking at that $3.6 billion legislation and think the Iron Dome funding should be handled separately from the unrelated, and politically fraught, child migrant issue.

In a bid to get strong backing from their party, House Republicans included no money for Iron Dome in their bare-bones supplemental, which focuses solely on the border crisis and includes immigration policy changes designed to win as much right-wing GOP support as possible.

The House could address the Iron Dome in a stand-alone bill, or as part of an anticipated continuing resolution in September to keep the government running for a few more months. But there is strong resistance in the House to using the supplemental as a vehicle for the appropriation for Israel.

Senate Minority Leader Mitch McConnell, R-Ky., is pushing for stand-alone legislation for the Iron Dome, stressing that Republicans are united in their support for Israel. McConnell’s plan would allow Republicans to show their support for Israel even if they remain at odds with Senate Democrats over their approach to addressing the immigration crisis.

“We hope our friends on the other side will join us in coming to a sensible, bipartisan solution that can be passed quickly,” McConnell said in a floor speech last week. “As most senators know, the Iron Dome missile defense system has played a critical role in defending Israel’s population from the rocket attacks launched by Hamas from within the Gaza Strip.”

Arizona Sen. John McCain, a senior Republican on the Armed Services Committee, said he thinks the Iron Dome funding would sail through the chamber on its own.

“We could take up $225 million on the floor of the Senate by unanimous consent today,” he said last week. “It would pass without objection.”

Senate Majority Leader Harry Reid, D-Nev., hinted Monday that the chamber could ultimately consider the Iron Dome separately from the migrant children funding, even as he filed cloture on the emergency supplemental with the funding for Israel intact, lining up a procedural vote for Wednesday. If the Senate did approve the Iron Dome funding separately from the migrant supplemental in the coming days, a move that seemed to be gaining traction on Tuesday, the House could follow suit, potentially paving the way for approval of the funding before the recess.

The Iron Dome, which was developed by Israel, has been paid for mostly by the United States. Indeed, both the Senate Appropriations Defense spending bill and the House-passed companion measure (HR 4870) would provide $351 million for it in fiscal 2015, nearly doubling the administration’s request.

The $225 million in the supplemental, which has been requested by Israel, would be in addition to that fiscal 2015 funding. If the two pending additional tranches of spending were enacted, they would bring to $1.28 billion the total of U.S. appropriations for the system.

The White House did not include the Iron Dome spending in its request for the supplemental. But Defense Secretary Chuck Hagel supports the appropriation.

“The government of Israel has requested $225 million in additional U.S. funding for Iron Dome to accelerate production of Iron Dome components in Israel in order to maintain adequate stockpiles,” Hagel recently wrote to congressional leaders. “The Department of Defense has reviewed and supports this urgent request.”

Given the urgent need for the missile defenses, Hagel also requested Congress not hold the supplemental spending to the terms of an agreement in March that would require more work on the Iron Dome program be done in the United States. The vast majority of the work on the program has been done in Israel.

“Israel will continue to develop co-production of Iron Dome components in the United States” per the March agreement, Hagel wrote. “However, Israel assesses that it will take another two to three years to reach full production capacity in the United States, which would not address Israel’s current shortfall.”

Lawmakers have long felt the United States needs to play more of a role in — and see benefits from — the Iron Dome program. Massachusetts-based Raytheon Co. would benefit most from domestic Iron Dome production.

Most recently, Senate appropriators included language in their report on the defense spending bill that would hold back half of the fiscal 2015 funding for Iron Dome until the Israeli Missile Defense Organization provides more information on the program, including a report documenting the transfer from Israeli industry to U.S. companies of all technical data packages required for U.S. production of Iron Dome.

In their version of the supplemental, Senate Democrats would provide some relief from that agreement, but it is unclear how lawmakers would handle the issue in any sort of a compromise measure.

Tamar Hallerman and Niels Lesniewski contributed to this report.