TOKYO (Reuters) - U.S. Secretary of State Rex Tillerson said on Thursday the State Department’s current spending was “not sustainable,” and he willingly accepted the “challenge” President Donald Trump had given in proposing to cut more than a quarter of his agency’s budget. Trump’s budget proposal for the fiscal year beginning on Oct. 1 would cut 28 percent of the budget for U.S. diplomacy and foreign aid, according to documents provided by the White House. The combined budget for the State Department and the United States Agency for International Development (USAID) would be $25.6 billion. Speaking in Tokyo at the start of a trip to Asia focused on the threat from North Korea, Tillerson defended the cuts as a necessary correction to a “historically high” budget that had grown to address conflicts abroad in which the United States was engaged, as well as disaster aid. “Clearly the level of spending that the State Department has been undertaking, particularly in this past year, is simply not sustainable,” he said. “As time goes by, there will be fewer military conflicts that the U.S. will be directly engaged in.” The United States will also reduce spending by attracting funds from other countries and “other sources” to contribute to development aid and disaster assistance, Tillerson said. Trump’s budget would preserve $3.1 billion in security aid to Israel but reduce funding for the United Nations, climate change and cultural exchange programs. For a graphic on winners and losers in Trump's budget, click here: here Congress, which rules on the government’s purse strings and is controlled by Trump’s fellow Republicans, may reject some or many of the cuts to the State and USAID budgets, which pay for everything from maintaining America’s diplomatic corps to fighting poverty, promoting human rights and improving health in foreign nations. More than 120 retired U.S. generals and admirals urged Congress in a letter last month to fully fund diplomacy and foreign aid, arguing the functions were “critical to keeping America safe.” Several Republicans in Congress have expressed opposition to Trump’s plans to slash funding for diplomacy and foreign aid. Senator Lindsey Graham, the Republican chairman of the Senate subcommittee responsible for those budgets, said last month the proposal would be “dead on arrival” in Congress.  Tillerson said there would be a “comprehensive examination” of how the State Department’s programs are executed and how the department is structured. He said the situation was challenging, but that he took on the challenge that Trump had given him “willingly.” “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,” he said.  