US Airways ( LCC) shored up the backing for its hostile bid to take over Delta Air Lines ( DALRQ), adding Morgan Stanley as joint lead arranger with Citigroup for a financing package.

US Airways said Monday that the commitment for $7.2 billion of debt financing had been revised to provide "significantly improved" financial terms, and the company indicated that it could secure even more funding.

In a prepared statement, CFO Derek Kerr welcomed Morgan Stanley into the group with Citigroup. "These two world-class firms, combined with the possibility for a third firm, reinforce the financial community's confidence in the value creation of our proposed merger with Delta," he said.

Analyst Helane Becker of Benchmark Company said the addition of new firms is a sign that the US Airways offer continues to have strong backing on Wall Street. "This is US Airways getting its ducks in a row, saying we have support," she said.

Becker noted that Delta's fate remains up to its creditors, whose central concern is learning when they'll see their money. Given the likelihood of a lengthy regulatory review and the opposition of Delta management, "I don't think it will be easy to get this done," she said. "But US Airways is saying we just want to give it a try, and if we get shot down, we will move on."