WASHINGTON 

The Senate on Thursday passed a $750 billion defense spending bill ahead of a vote on an amendment that would block the president from using funds to attack Iran without congressional approval.

Senators voted 86-8 on the National Defense Authorization Act, which also provides broad policy outlines for the Pentagon.

The legislation includes a base budget of around $642 billion for the Pentagon along with $23 billion for the Department of Energy's national security programs.

About $76 billion will also go to the overseas contingency operations fund -- sometimes referred to as war funds -- which operates as a separate pot of funding for the Department of Defense and State Department and has little congressional oversight.

In addition to the bill, the Senate will be voting Friday on an amendment to the legislation which would block President Donald Trump from using funds to carry out military action against Iran without congressional approval.

The vote on the amendment comes amid turbulent times in U.S.-Iran relations after the Iranian military shot down an American drone earlier this month.

Iran claims it was flying in Iranian territory, while the U.S. says it was in international airspace.

Trump responded by imposing sanctions on Iran's Supreme Leader, Ali Khamenei.

Tensions have been rising between the U.S. and Iran since May 2018, when Washington unilaterally withdrew from a landmark 2015 nuclear deal between Tehran and the five permanent members of the UN Security Council plus Germany and the European Union.

The U.S. has since embarked on a diplomatic and economic campaign to put pressure on Iran in order to renegotiate the agreement.

As part of its campaign, the U.S. has re-imposed sanctions on exports of Iranian crude oil, which has sent Iran’s economy into a nosedive.