Rarely a week goes by without President Trump trying to open a new front in the trade war (Europe, Japan, South Korea and Mexico have all been threatened with new levies), and this sleepy post-holiday week is no exception.

In a tweet, President Trump hinted at the possibility of new tariffs on Indian imports, saying that the US would no longer stand for India's overly aggressive tariff regime.

India has long had a field day putting Tariffs on American products. No longer acceptable! — Donald J. Trump (@realDonaldTrump) July 9, 2019

To be sure, there are ulterior motives here, trade is probably a secondary issue. With Narendra Modi emboldened by his recent re-election, India has decided to move ahead with the purchase of a Russian missile defense system - which, by law, gives Washington the right to slap sanctions on India, which it has threatened to do - and its also refused to yield to America's ban on Iranian oil exports.

Given this, it's hardly a surprise that Trump is trying to get the Indians back in line.