India, July 6 -- US President Donald Trump said on Friday he has signed letters to 12 countries outlining tariff levels they will face in what he described as "take it or leave it" offers, with the communications set to go out on Monday.

Speaking to reporters aboard Air Force One, Trump declined to name the countries involved. He also raised the stakes, saying tariffs could now reach as high as 70% - up from previously threatened levels of 50% - with most set to take effect August 1.

"I signed some letters and they'll go out on Monday, probably twelve," Trump said, according to news agency Reuters. "Different amounts of money, different amounts of tariffs."

India appears likely to be among the 12 countries receiving the letters, accord...