The difficulties follow the collapse of Wolverhampton-based Carillion in January this year.
Interserve, which is in re-financing talks, issued a statement saying: "The fundamentals of the business are strong and the board is focused on ensuring Interserve has the right financial structure to support its future success."
The group, which has a worldwide workforce of around 75,000 including 2,000in the West Midlands, says that options included bringing new capital into the business and progressing the disposal of non-core businesses.
Interserve has its new regional office near Birmingham Airport and employs hundreds at nursing agency Interserve Healthcare in Telford and in cleaning and maintenance at Russells Hall Hospital, Dudley.
It also owns specialist construction firm RMD Kwikform in Aldridge and has offices in West Bromwich.
A re-financing deal could see creditors take control of the group.
Interserve warned in November that its debt would rise more than expected this year following delays to projects and the weak construction market.
Labour has called for temporary ban on Interserve bidding for public contracts
The party's shadow minister for the Cabinet Office, Jon Trickett, said: "The Government has once again dropped the ball on outsourcing and it's the public who will suffer.
"Less than two weeks ago, I asked the Government what extraordinary steps they are taking to monitor the financial health of Interserve.
"They told me they 'do not believe that any strategic supplier is in a similar situation to Carillion', and in November Interserve continued to win public sector contracts worth millions, despite effectively being insolvent.
"The Tories’ outsourcing and privatisation obsession is putting our public services and taxpayers’ money at risk. The Government must take urgent steps to ensure all existing contracts with Interserve are reviewed and that they are prevented from bidding for public sector contracts until they have proved they are financially stable and there is no risk to the taxpayer."