Carl Icahn and the Trump Taj Mahal workers’ union failed to reach a compromise deal, putting Atlantic City’s second-biggest casino thisclose to shutting down, sources told The Post.

Trump Entertainment Resorts, the Taj’s parent, had given the union until Monday at 5 p.m. to drop its appeal of a Delaware court ruling allowing the casino to break the collective-bargaining agreement with the union.

The two sides on Monday were no longer in active discussions, a source close to the situation said.

“I think the union believes Carl will back down, but I don’t think he is going to,” a source close to the deal said.

The union is expecting that Icahn, who owns all of the casino’s senior debt, will provide roughly $30 million in bankruptcy financing.

Trump Entertainment had set a hard Dec. 20 date for shutdown of the casino, and was working with Atlantic City’s Division of Gaming Enforcement to start removing slot machines later this week.

The Division needs to know by Wednesday whether to proceed with the shutdown.

In November, the Taj saw revenue fall 13 percent as it stopped extending credit to customers or taking hotel reservations because of the possible shutdown. Four of Atlantic City’s 12 casinos have closed this year, and The Taj would be the fifth.

In Trenton, Icahn did not receive the $150 million in tax breaks he sought for the casino, thereby making saving it a more difficult choice, sources said.

Gov. Chris Christie and N J State Senate President Stephen Sweeney (D-Gloucester) met late last week and spoke about saving the Taj but are not going to move forward until next month, at the earliest, a source said.

“Neither Christie nor Sweeney wants to be seen as giving Carl a bailout,” said the source.

Icahn has given in on the union’s demand for continued health-care benefits but is reluctant to concede on work-rule changes like the right to outsource restaurant workers, sources said.