Former Arizona Gov. Jan Brewer called President Trump’s proposal to dump illegal immigrants into sanctuary cities a “great plan” on Monday.

“When I was Governor, illegal aliens cost AZ taxpayers $1.6 billion/yr in education, health care and incarceration costs. So, why do we continue to bear these costs when sanctuary cities encourage illegal immigration? Great plan by @realDonaldTrump to utilize those cities!” the Republican tweeted.

Trump tweeted Friday he had put new immigration plan under “consideration.”

“Due to the fact that Democrats are unwilling to change our very dangerous immigration laws, we are indeed, as reported, giving strong considerations to placing Illegal Immigrants in Sanctuary Cities only,” Trump said. “The Radical Left always seems to have an Open Borders, Open Arms policy – so this should make them very happy!”

Trump was later asked to clarify his comments. He said states like California should get an “unlimited supply” of illegal immigrants and see if they would still be happy.

"We'll bring them to sanctuary city areas and let that particular area take care of it, whether it's a state or whatever it might be," Trump said. "California certainly is always saying, 'Oh, we want more people.' And they want more people in their sanctuary cities. Well, we'll give them more people. We can give them a lot. We can give them an unlimited supply, and let's see if they're so happy."

The proposal was reportedly suggested by top Trump immigration adviser Stephen Miller, but it was initially rejected because of “PR risks,” according to a top Immigration and Customs Enforcement official.

Back in 2010, Brewer oversaw the passage and enforcement of the immigration law known as Arizona SB 1070, including the controversial “ show me your papers ” provision, which at the time was the toughest immigration law in the country.

[ Opinion: The double danger of Trump's proposal to drop migrants in sanctuary cities]