The fiscal 2020 defense budget bill, including a 3.1% military pay raise, cleared a Senate hurdle last week, setting up a battle in the House over spending and policy regarding Iran.

The Senate voted 86-8 June 27 to pass a $750 billion version of the National Defense Authorization Act under an unusual procedure set up by Senate Majority Leader Mitch McConnell, R-Kentucky, to address the bill before Congress went into recess for Independence Day.

McConnell also allowed a June 28 vote on an amendment that would have limited President Donald Trump's authority to use military force against Iran by requiring Congressional approval. The vote on the amendment, sponsored by Sens. Tom Udall, D-New Mexico, and Tim Kaine, D-Virginia, was 50-40. But the measure ultimately lacked the 60 votes it needed to pass under Senate rules.

Although the amendment failed, Udall and Kaine said in statements that the vote sent a signal to the House to continue efforts to pass a similar measure that would block Trump from unilateral action against Iran.

"The debate doesn't end here. The House now has an opportunity to pass this amendment," Kaine said.

Differences in the Senate and House versions of the NDAA would have to be worked out in a House-Senate conference committee.

Trump has repeatedly stated that he does not need Congressional approval to protect U.S. troops and interests in the region -- and that his priority is preventing Iran from developing nuclear weapons.

The version of the NDAA passed by the Senate called for $750 billion in spending. House Armed Services Committee Chairman Rep. Adam Smith, D-Washington, has proposed $733 billion, which would include the 3.1% pay raise for troops.

House Democrats have also lined up for floor debates on Iran; the proposal for a new low-yield nuclear weapon for the Navy; the impact of climate change on the military; transgender individuals serving in the military; and the funding of Trump's controversial southern border wall.

More than 100 House Democrats sent a letter to Trump last week warning that he lacks authority to use force against Iran without coming to Congress first.

Article 1 of the Constitution "places the power to declare war and authorize offensive military force solely with Congress," the letter said.

"The current authorization for the use of military force (AUMF), passed by Congress in 2001, does not provide the authority to engage in military action against Iran," the letter said.

In a separate statement, Rep. Jason Crow, D-Colorado, who joined in the letter, renewed his call to set up a military-to-military hotline between Iran and the U.S. to avoid miscommunication that could lead to war.

"We cannot afford to stumble into war with Iran or allow a misunderstanding between our forces to escalate into conflict," Crow, a former Army captain and Ranger who served tours in Iraq and Afghanistan, said.

Trump and Secretary of State Mike Pompeo have said they are prepared to negotiate with Iran without "preconditions," but Iran's ambassador to the United Nations, Majid Takht Ravanchi, said Sunday that talks could not be considered while the U.S. continues to threaten Iran.

In an appearance on CNN's show "Fareed Zakaria GPS," Ravanchi said the first thing the U.S. should do is return to its nuclear agreement with Iran, the Joint Comprehensive Plan of Action. Trump withdrew the U.S. from the JCPOA last year, saying the agreement was too weak to effectively limit Iran's nuclear aspirations, and that the country wasn't abiding by it anyway.

-- Richard Sisk can be reached at Richard.Sisk@Military.com.