Senior administration officials have begun drafting sanctions against Iraq after President Trump publicly threatened the country with economic penalties if it proceeded to expel U.S. troops, according to three people briefed on the planning.

The Treasury Department and White House would likely play a lead role if the sanctions are ultimately implemented, the officials said. Such a step would represent a highly unusual move against a foreign ally that America has spent almost two decades and hundreds of billions of dollars supporting.

The officials, who spoke on the condition of anonymity because they were discussing internal deliberations, stressed that talks were preliminary and that no final decision has been made on whether to impose the sanctions.

One of the officials said the plan was to wait “at least a little while” on the sanctions decision to see whether Iraqi officials followed through on their threat to push U.S. troops out of the country.