Continental Airlines’ year-long bid to co-operate with United Airlines and its global allies on transcontinental ventures has hit a late snag in Washington, as US antitrust regulators sought to add restrictions ahead of the proposed alliance’s final approval.

Department of Justice officials remain in talks with their counterparts at the Department of Transportation, which granted the venture its preliminary acceptance in April, on the terms of the government’s final order, people familiar with the matter said on Tuesday.