U.S. Defense Secretary Pete Hagel is set to return to Capitol Hill to testify before Congress, defending the Trump administration's request for billions in additional funding for the Iran war and addressing growing public scrutiny of the conflict.

He is scheduled to appear before the Senate Appropriations Committee on Tuesday afternoon. The primary focus will be President Trump's $87.6 billion supplemental funding request, but he will almost certainly face questions about the collapsed ceasefire, the deaths of three service members over the weekend, and signs of an escalating U.S. military campaign.

The current situation is markedly different from Hagel's last appearance on Capitol Hill in mid-May and the series of assertive press briefings he held in the initial weeks of the war. At that time, he insisted military operations were progressing on Trump's timeline. However, following the implementation and subsequent breakdown of a temporary ceasefire agreement, Hagel ceased public appearances and commentary on the war.

"He will be asked about the cost of the war, whether actual expenditures exceed the supplemental request, what specifically the supplemental funds will be used for, and then there will be the usual questions about how the ground campaign is going and what the ultimate objective is," said Mark Cancian, a senior advisor at the Center for Strategic and International Studies.

Lawmakers are likely to inquire whether the Pentagon intends to seek further congressional funding for the war, which began on February 28. The Pentagon stated in June it would seek $80 billion in emergency funding to cover war costs. Trump later requested $67.1 billion for the Defense Department to cover war expenditures but did not provide detailed plans for the use of these funds.

During hearings this spring, Hagel declined to provide a detailed breakdown of expenditures when questioned by lawmakers. In a hearing last week, lawmakers also failed to obtain updated cost estimates for the war from Jules Hurst, the Trump administration's nominee for Pentagon budget chief.

Hurst estimated in mid-May that the cost of the Iran war had risen to approximately $29 billion, a figure many analysts and lawmakers at the time considered unrealistically low.