NEW YORK — Lawyers for American Airlines pressed Bankruptcy Judge Sean Lane to approve its plan to merge with US Airways and exit bankruptcy protection, but Lane delayed a ruling because of the federal government’s lawsuit against the merger.This was supposed to be American’s victory lap — the day Lane, who has overseen the Chapter 11 bankruptcy reorganization since November 2011, would approve the merger making American the world’s biggest airline. Instead, it was a sideshow. The Justice Department ruined American’s plans, at least temporarily, on Tuesday by filing a lawsuit against the merger. The government and attorneys general from six states, including Texas, argued that the deal would hurt competition and increase prices for consumers by leaving four airlines controlling more than 80 percent of the U.S. market. In court Thursday, lawyers for Fort Worth-based AMR Corp., American’s parent, and its unsecured creditors said the Justice Department’s case shouldn’t stop the bankruptcy judge from approving the reorganization plan. But Lane said he had “lingering doubts” and delayed a decision until at least Aug. 29 when the next hearing is set.At the start of the hearing, he said he considered adjourning it before deciding to move ahead, because calling it off might have led to “unhelpful confusion or uncertainty.” Instead, he asked for briefs on the impact of the antitrust case on the standards for approving the plan and the appropriateness of ruling on the plan before the U.S. case is resolved. He said any party can file a brief, including the Justice Department, through Aug. 23.American and US Airways had hoped to close their merger by late September, but executives for both companies say that’s unlikely. They vowed to fight the Justice Department in court, but that could take months.If the government wins, AMR could be forced to dust off a plan to emerge from bankruptcy as a stand-alone company. That could push the process into 2014. The merger was supposed to cap an era of consolidation that has helped the airline industry limit seats, raise prices and return to profitability. Although it would leave one fewer airline, American and US Airways argued that their merger would increase competition by creating a stronger rival for industry leaders United Airlines and Delta Air Lines. Lane also delayed a ruling on a $20 million severance award for AMR CEO Tom Horton, who would serve briefly as chairman before leaving the new company. The U.S. trustee’s office, which oversees bankruptcy cases for the Justice Department, said the payment violates bankruptcy law limits designed to prevent executives from getting big rewards not available to regular employees. Susan Golden, a lawyer for the trustee, said the new company shouldn’t bear the cost of paying Horton for work he did on AMR’s reorganization. “He’s being paid for work already performed,” she said. But Stephen Karotkin, a lawyer for AMR, said creditors and shareholders approved the merger knowing that it contained Horton’s payment. He said the payment in cash and stock would ensure that Horton sticks around long enough to help smooth the process of combining two airlines.