Three Senate chairmen are demanding to know exactly how much President Obama’s executive amnesty will cost and where that money will come from.

In a letter to U.S. Citizenship and Immigration Services’ Chief Financial Officer Joseph Moore, released Tuesday, the chairmen expressed concern about funding for USCIS’ main duty — to oversee lawful immigration in the United States — and the impact executive amnesty would have on that responsibility.

“The President’s directives will redirect scarce resources from [USCIS’] core mission to activities that Congress has never approved, and will very likely jeopardize the financial health of the agency,” the three GOP senators wrote. “If USCIS has a budget shortfall, the agency will no doubt ask the taxpayers to shoulder the burden.”

The three chairmen who signed onto the letter include Immigration Subcommittee Chairman Jeff Sessions (R-AL), Judiciary Committee Chairman Chuck Grassley (R-IA) and Homeland Security Chairman Ron Johnson (R-WI).

In November, President Obama announced — among other orders — an expansion of the Deferred Action for Childhood Arrivals program and the extension of a new amnesty to illegal immigrant parents of citizens and lawful permanent residents.

According to Sessions, Grassley and Johnson, the executive actions “raise serious legal questions and may have significant budgetary consequences.”

In their letter, dated January 22, the trio call on Moore to provide a “detailed accounting of all expenditures by USCIS to date and a projection of all temporary and permanent expenditures for these executive actions, including the source of the funds to be used and the specific accounts in which the funds are located, in dollar amounts.”

The demands come as the Senate is expected to take up a Department of Homeland Security funding bill. The House passed a DHS appropriations bill earlier this month that blocks funding for Obama’s executive amnesty. There are questions, however, about the level of support Republicans will be able to muster to pass a defund bill in the Senate.

Funding for DHS expires on Feb. 27.

Read the full letter: