Donald Trump on Tuesday vowed to immediately repeal and replace President Barack Obama’s signature health care law if he’s elected president next week.

“When we win on Nov. 8 and elect a Republican Congress, we will be able to immediately repeal and replace Obamacare. We have to do it,” Trump said Tuesday afternoon in an address on the Affordable Care Act in King of Prussia, Pennsylvania.

“I will ask Congress to convene a special session so we can repeal and replace,” he continued. “And it will be such an honor for me, for you and for everybody in this country because Obamacare has to be replaced. And we will do it, and we will do it very, very quickly. It is a catastrophe.”

But Congress won’t be able to repeal and replace the health law quickly or easily. Even if Republicans keep control of the Senate, Democrats will likely have enough votes to filibuster a quick repeal bill.

While Republicans are working on a repeal using a complicated budget procedure that doesn’t allow a filibuster, it would likely take months to enact. And a replacement bill may be even harder.

House Speaker Paul Ryan has released a blueprint of a replacement plan, but Republicans are divided on the details of how to reform the massive health care system.