Federal Reserve Chairman Jerome Powell testifies before a House Financial Services Committee hearing on the “Semiannual Monetary Policy Report to Congress," at the Rayburn House Office Building in Washington, U.S., July 18, 2018.

The head of the U.S. central bank has some concerns about reducing immigration to the U.S.

Doing so could stunt growth the labor force and therefore hurt the U.S. economy long term, Fed Chairman Jay Powell said in a letter to a Democratic senator, seen by Bloomberg News.

Sen. Catherine Cortez, D-Nev., asked if Powell agreed with his colleague, Minneapolis Fed President Neel Kashkari, on the topic. Kashkari wrote in a January Wall Street Journal column that immigration is "as close to a free lunch as there is" for the U.S. economy. Kashkari's parents came from India and his wife is from the Philippines.

"From an economic growth standpoint, reduced immigration would result in lower population growth and thus, all else equal, slower trend economic growth," Powell wrote in the letter, according to Bloomberg.

The comments are a stark contrast from President Donald Trump's take on immigration, a divisive issue ahead of midterm elections next week. Since campaigning in 2016 to build a wall with Mexico, the president has categorized immigration as a threat and a burden to taxpayers.

His latest hard-line proposal was a plan this week to do away with birthright citizenship for children born to noncitizens and undocumented immigrants. The White House deployed U.S. troops to the border to support Customs and Border Protection agents preparing for the arrival of a caravan of an estimated 4,000 migrants. Trump said the total U.S. troops could reach 15,000 — roughly double the number the Pentagon said it currently plans for a mission.

— Read the full Bloomberg report here.

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