Marine underwriters are facing a possible $900m payout on up to 50 ships caught up in the conflict in Ukraine as hopes of an immediate safe way out appear to be fading.

One month into Russia’s invasion, the prospect is emerging that many of the vessels will be stuck at Ukrainian ports for an extended time. Under war risk terms, underwriters will have to pay out on a total loss if ships are trapped for six or 12 months.

International efforts to find a safe passage out appear to have foundered.