The US House of Representatives passed a $1.15tn defense policy bill in a near-party-line vote on Wednesday, after Democrats refused to back the measure amid the war with Iran and Donald Trump’s push to impose new restrictions on voting nationwide.

A key plank of the president’s plan to spend $1.5tn on the military in the 2027 fiscal year, the National Defense Authorization Act (NDAA), passed the Republican-controlled chamber by a 216-212 vote, with all but six Democrats opposing its passage. Seven House Republicans broke ranks to oppose it. The measure now goes to the Senate.

Congress passes the NDAA each year with bipartisan margins, with the measure’s high cost seen as necessary to make generational investments in the military.

“For the first time in 40 years, we’ve been presented a budget that accounts for the true cost of American deterrence. This topline begins to reverse the damage caused by decades of underinvestment in the US military,” Mike Rogers, the House armed services committee chair, said before the vote.

But the path to enactment for this year’s NDAA has been complicated by the president’s decision to join Israel in attacking Iran without first seeking authorization from Congress. Last week, Senate Democrats blocked the advancement of that chamber’s version of the NDAA in protest of the war, which has flared anew after a memorandum of understanding meant to spur peace talks collapsed.

Democrats also soured on the bill after Mike Johnson, the Republican House speaker, acceded to the demands of rightwing lawmakers and inserted into the legislation the Save America Act, a Trump-backed proposal to ban mail-in ballots and impose new identification restrictions on voters at the polls and when they register.

The twin dynamics combined to make the Democrats’ opposition nearly unanimous two days before House lawmakers are scheduled to depart Washington DC for a recess that stretches until the end of August.

Another sticking point for Democrats was the measure’s overall cost of $1.15tn, and the plan to slash funding elsewhere in the government a year after Congress’s Republican majorities approved extending an array of lower tax rates indefinitely.

“Our country faces threats and DoD has modernization needs, but I cannot and do not support meeting these needs by making massive cuts to critically important domestic programs and slashing taxes,” said Adam Smith, the top Democrat on the House armed services committee.

“We need to be more fiscally responsible and DoD needs to become more innovative and efficient in terms of developing capabilities to meet our national security needs in a more cost-effective manner.”

Amid a wider backlash within the party over US support for Israel, some Democrats said they opposed the NDAA because of its inclusion of provisions that would deepen cooperation between the two countries’ defense industries.

“This amendment is an existential threat to American sovereignty and democracy,” said the progressive congresswoman Alexandria Ocasio-Cortez, who was among the no votes.

The House’s passage of the bill came after the chamber considered dozens of amendments. While many were agreed to unanimously, others offered barometers for how far the Republican-controlled chamber was willing to go on the most divisive issues before the parties.

A proposal by Republican Eli Crane to halt all military aid to Ukraine was resoundingly defeated by a 76-350 vote, while an amendment from Republican Lauren Boebert to codify Trump’s executive order banning transgender service members failed by a 212-217 tally.

However, the House agreed to amendments from Nancy Mace barring the military health insurer from offering some gender-related care, and banning transgender athletes from girls’ sports at defense department-run schools.

Beyond the NDAA, House Republicans are also moving forward with a party-line attempt to authorize $60bn in new military spending, much of which is expected to cover costs related to the war with Iran. But that proposal falls far short of the $350bn the Pentagon originally proposed to bring overall defense spending to $1.5tn for the upcoming fiscal year.