US President Donald Trump once left Indian Prime Minister Narendra Modi shocked and concerned by telling him India and China didn't share a border, a new book by two Pulitzer-winning journalists claims, according to media reports.

"It's not like you've got China on your border," Trump told Modi, and the Indian premier's eyes "bulged out in surprise", Washington Post journalists Phillip Rucker and Carol Leonning report in A Very Stable Genius, according to the US newspaper.
The book's title is a shout-out to Trump's own description of his mental acumen.
Rucker and Leonning write that Prime Minister Narendra Modi's expression "gradually shifted, from shock and concern to resignation" after Trump's remarks, and that one of the US president's aides felt Modi probably "left that meeting and said, 'This is not a serious man. I cannot count on this man as a partner'," the Post reports.
The aide told the book's authors that India "took a step back" in its diplomatic ties with Washington after that meeting.
Donald Trump's knowledge of the subcontinent's geography has come under scrutiny before.
A TIME magazine correspondent wrote last year that the US president had to be corrected at a briefing where he said he knew Nepal and Bhutan were in India, reports India Today.
Trump also reportedly "mispronounced Nepal as 'nipple' and laughingly referred to Bhutan as 'button'," according to the Indian magazine.