The Trump administration this week stepped up its ambitious effort to replace about $1.6 trillion in lost tariff revenue that was eliminated by the Supreme Court’s decision to strike down a range of the president’s import taxes.

Recovering that lost revenue, which the White House was counting on to help offset the steep, multi-trillion dollar cost of its tax cuts, is possible but will be challenging, experts say.

The administration has to use different legal provisions to impose new duties, and those provisions require longer, complex processes that U.S. companies can use to seek exemptions. It could be months or more before it is clear how much revenue the replacement tariffs will yield.