Washington (CNN) Senate Democrats urged President Donald Trump to revise the proposed refugee ceiling of 18,000, a figure which would be a historic low, in a letter addressed to the President Friday.

"We ask that you to immediately reverse course and heed the recommendation of top US military officials and faith leaders to open our doors to eligible refugees from all corners of the world," the letter reads. "A generous US refugee policy spares tens of thousands from terrible fates."

The letter, led by Sens. Jeff Merkley and Ed Markey, comes on the heels of the State Department's report to Congress that proposed a refugee cap -- which dictates how many refugees may be admitted to the US -- to 18,000 for fiscal year 2020, which begins next week.

Under Trump, the administration has slowly chipped away at the refugee cap. The ceiling for fiscal year 2019 stands at 30,000, which, at the time, was the lowest level since 1980.

The State Department announced the proposed refugee ceiling Thursday as part of a larger number of combined refugee and asylum claims expected for the next fiscal year.

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