US President Donald Trump has blocked the $US121 billion takeover of Qualcomm by Singapore's Broadcom over national security concerns.
The takeover of the telecommunications company would have been the most expensive to occur in the technology industry.
"There is credible evidence that leads me to believe that Broadcom ... through exercising control of Qualcomm ... might take action that threatens to impair the national security of the United States," a White House statement quoted Trump as saying.
