Secretary of State Rex Tillerson on Thursday went to bat for President Donald Trump, defending the administration’s proposed cuts to the State Department’s budget.

“Clearly the level of spending that the State Department has been undertaking, particularly in this past year, is simply not sustainable,” Tillerson said in Tokyo, according to Reuters. “As time goes by, there will be fewer military conflicts that the U.S. will be directly engaged in.”

Trump’s budget blueprint proposes cutting the State Department’s budget by 28 percent. However, his budget is merely a proposal and Congress will have a large role in shaping government spending. Trump’s proposed spending cuts will likely face an uphill battle in Congress, and several prominent Republicans have already spoken out against major cuts at the State Department.

Tillerson said on Thursday that he’s ready to take on Trump’s “challenge” to slash the budget at the State Department.

“I’m confident that with the input of the men and women of the State Department we are going to construct a way forward that allows us to be much more effective, much more efficient and be able to do a lot with fewer dollars,” Tillerson said, per Reuters.