Trump pledged on Friday that he is prepared to slap $267 billion in tariffs on Chinese products, in addition to the $200 billion he has already promised.
The U.S and China have been locked in an escalating trade dispute, with each nation levying significant tit-for-tat tariffs against one another. But disagreements between the two major economic powers run deeper than just the trade balance and tensions remain over limits on USA firms' access to Chinese markets, intellectual property protection, technology transfers, and investment.
Singapore slipped 0.6 percent and Taipei shed 1.1 percent, while Bangkok and Jakarta were also sharply lower.
On top of that, strong U.S.jobs numbers on Friday had bolstered bets on a higher dollar on expectations the Federal Reserve will keep raising US interest rates.
But Tokyo and Seoul both ended 0.3 percent higher.
The auto-sector market economist Jon Gabrielsen told the Detroit Free Press that Trump's tweet was "further evidence that neither the president nor his trade representatives have any clue of the complexities of global supply chains".
MSCI's broadest index of Asia-Pacific shares outside Japan fell 0.9 percent to the lowest since July 2017, extending losses from last week when it dropped 3.5 percent for its worst weekly showing since mid-March.
Investors are also on the edge about any contagion risks from turmoil in some emerging markets (EM) including Argentina and Turkey whose currencies have been routed recently.
In August, China unveiled a proposed list of retaliatory tariffs on $60 billion of U.S. goods ranging from liquefied natural gas to some types of aircraft, should Washington activate the tariffs on its $200 billion list.
Chinese shares were battered with the blue-chip index off 1.4 percent.
The Australian dollar, a proxy for Chinese growth because of the large amount of metals it sells there, hovered near its lowest in 2 1/2 years and was last at $0.7115.
The president's comments Friday added to the uncertainty on trading floors, which have also been hit by concerns of a brewing financial crisis in emerging markets.
In commodities, oil prices were firmer after three straight days of losses, with USA crude futures up 44 cents at US$68.19 per barrel.
Spot gold was a tad softer at $1,193.01.