Brightline has reached a deal with municipal-bond insurer Assured Guaranty Ltd. that would provide the debt-laden Florida railroad with at least $350 million in new loans if it heads into Chapter 11 bankruptcy, according to people familiar with the matter. The move underscores a growing sense of urgency from Fortress Investment Group-backed Brightline to address its $5.5 billion of obligations.

Its deeply distressed bonds have languished for months as municipal-debt firms and hedge funds that hold the railway's corporate debt have jockeyed for the best position in a major restructuring that has long been seen as inevitable. The pre-arranged financing signals that Brightline is preparing for a potential court-supervised process rather than an out-of-court workout.

The deal with Assured Guaranty Ltd. would give Brightline liquidity to continue operations during a Chapter 11 case. Holders of the railroad's corporate debt have been negotiating for months over how losses will be distributed, with bond prices reflecting deep skepticism about recovery prospects.