Several Democratic lawmakers are voicing opposition to a potential request for increased Pentagon funding in light of the Iran war, arguing that the Trump administration has not clearly defined its goals or expectations for how long the war may last, CNN reports.

Congress last year authorized nearly $900 billion for military programs as part of a bipartisan package to fund the Defense Department for this fiscal year. But the Trump administration has briefed legislators on a potential need for more money in a conflict analysts estimate is costing American taxpayers more than $890 million per day.

"At this particular moment, the administration has been unable to make its case with respect to the wisdom or justification of this war in the Middle East," House Minority Leader Hakeem Jeffries told NBC News.

Even after Trump administration briefings with legislators, it remained unclear how much money the Pentagon might request, when that request would come, and how long officials believe the war will last. The chances of advancing a package with the required 60 votes in the Senate are also uncertain, as some Democrats have indicated they are categorically opposed.