"He is now in Walter Reed Medical Center", he added.
When he was a CNBC contributor before taking the White House job, Kudlow argued the metals tariffs Trump had announced would harm consumers. While he had the backing of Treasury Secretary Steve Mnuchin, he was ultimately overruled by Robert Lighthizer, the US trade representative. Though he has always been opposed to tariffs, he has supported Trump's decision to erect tariffs against both China and key United States allies like Canada, Mexico and the European Union, calling them a useful tool.
Last week, Mr. Kudlow floated the possibility of dividing NAFTA talks and cutting separate bilateral deals with Canada and Mexico.
Mr Kudlow is the White House's economic adviser - and in recent days, made remarks that helped ratchet up tensions following the G7 summit. "Canadians, we're polite, we're reasonable, but we also will not be pushed around". President Trumptweeted that Kudlow suffered a heart attack and is hospitalized at Walter Reed Medical Center.
In the 1980s, he served as White House budget director under President Ronald Reagan and is still a champion of that era's conservative, supply-side economics, which calls for cutting taxes to boost growth - an ideology the Trump administration has emphatically embraced.