The U.S. and 11 other nations have come up with a trade deal after years of negotiations. But what's in it, who hates it, and what happens next? (Gillian Brockell/The Washington Post)

The Obama administration may have completed the arduous international negotiations needed to seal the 12-nation Pacific Rim trade deal, but there is a long road ahead before it gets approved by Congress.

The Trans-Pacific Partnership (TPP) is being hailed by supporters as the most extensive trade agreement in a generation and Obama hopes it will be a key economic achievement of his presidency.

[Deal reached on Pacific Rim trade pact in boost for Obama economic agenda]

But it could take a while to get it through Congress with aides not expecting votes on the trade pact to start until early April, though even that timing is very fluid.

The timeline for congressional consideration of the agreement is laid out in the law enacted earlier this year giving the president fast-track Trade Promotion Authority (TPA) powers, under which the deal is subject to a simple up or down vote and lawmakers can not amend or filibuster the pact.

The first steps are expected to begin later this week when the White House formally sends Congress a notice of intent to sign the agreement, which kicks off a 90-day waiting period. Congress gets to spend the first 30 days of that time privately reviewing the documents and consulting with the administration.

Next comes the public phase. The full trade deal will be open for anyone to review for 60 days, allowing interest groups to provide feedback. This window will provide critical insight into how much popular support the deal may receive. A poor reception during the public phase could make it difficult for Obama to rally support when it comes time for Congress to vote.

The next step will be for the U.S. International Trade Commission to conduct a full economic review of the deal. The agency has up to 105 days to complete that work but the process could take much less time.

Once the implementing bill is introduced in the House and the Senate, Congress has a maximum of 90 days to approve or disapprove the trade deal but can move much more quickly.

The reactions from lawmakers on Monday was indicative of the challenges the administration faces in the weeks and months ahead as skeptics in both parties were quick to express their concerns.

“[E]verything we know about the agreement suggests it will be yet another disaster for hard working American families,” said Rep. Rosa DeLauro (D-Conn.), who led the unsuccessful fight against the fast-track bill earlier this year. “The TPP will force American workers into competition with cheap third world labor in places like Vietnam, where independent unions are banned and the minimum wage is 56 cents an hour.”

DeLauro said the deal also fails to protect consumers from unsafe seafood, would increase drug prices and does not do enough to protect victims of human trafficking.

And many of the Republicans who reluctantly agreed to support Obama’s bid for fast-track authority have also stopped short of offering their support for the final Pacific Rim deal.

“Closing a deal is an achievement for our nation only if it works for the American people and can pass Congress by meeting the high-standard objectives laid out in bipartisan Trade Promotion Authority,” Senate Finance Committee Chairman Orrin Hatch (R-Utah) said in a statement. “While the details are still emerging, unfortunately I am afraid this deal appears to fall woefully short.”