General Motors' Opel unit could go bankrupt but this would be the worst possible scenario, the premiers of North-Rhine-Westphalia (NRW) and Opel's home state of Hesse said on Monday.

Hesse's Roland Koch and NRW premier Juergen Ruettgers told reporters they could not rule out any option for Opel, including insolvency. But Ruettgers said he did not expect the German carmaker to become insolvent.

He added he was pleased that Canadian car parts group Magna and rival bidder Fiat were ready to improve their offers. Ruettgers said he expected a decision on a preferred Opel bidder by mid-week.

(Reporting by Thorsten Severin, Writing by Sarah Marsh)