Billionaire Microsoft founder Bill Gates is urging British leaders not to back down from their commitment to foreign aid, saying it could cost lives in Africa. Gates on Wednesday was in London, where campaigning has started for early elections called by Prime Minister Teresa May. May has so far declined to say whether she will heed calls by fellow Conservatives to slash British foreign aid as part of her party platform. Gates told the Guardian newspaper Wednesday that a British refusal to commit itself to targeted spending on foreign aid could hurt efforts to wipe out malaria in Africa. "The big aid givers now are the U.S., Britain and Germany … and if those three back off, a lot of ambitious things going on with malaria, agriculture and reproductive health simply would not get done," he said. Gates said British funding has made an "absolute phenomenal difference" in eradicating tropical diseases that affect more than 1 billion people. Many conservatives want the government to spend more money at home to combat domestic crises. Some also contend that foreign aid money is frequently squandered. Gates said as a business executive who spends $5 billion a year helping developing nations, he hates wasting money. But he told an audience of British politicians and diplomats that no country can "build a wall to hold back the next global epidemic," and that foreign aid combats socioeconomic problems "at the source."