Donald Trump has vowed to freeze $US2.2 billion ($3.5 billion) in grants to Harvard University and remove its tax exemption status, amid a policy clash between the Ivy League school and the White House. The funding freeze comes after the institution chose to defy the Trump administration's demand it end diversity programs, alter hiring and admissions policy and limit activism on campus. Mr Trump had also called for broad governance and leadership reforms at the university. The US government said almost $US9 billion in grants and contracts in total were at risk if Harvard did not comply. Harvard President Alan...