P&O Ferries has suspended all sailings ahead of a "major announcement".
A statement which appears to be from the ferry operator said it "will be making a major announcement today (Thursday)."
This will "secure the long-term viability of P&O Ferries", it added.
The statement continued:
"To facilitate this announcement all our vessels have been asked to discharge their passengers and cargo and standby for further instructions.
"This means we're expecting all our ports to experience serious disruption today."
P&O Ferries wrote on Twitter that those hoping to travel will be guided to an alternative operator with services "unable to run for the next few hours."
The company, which transports passengers and freight, is owned by Dubai-based logistics giant DP World.
The transport secretary Grant Shapps says his officials will be having "urgent discussions" with the firm, which denies it's going into liquidation.
All its ships are remaining in port - causing major travel distruption.
It runs services between the UK, France, Ireland and the Netherlands.
*UPDATED
*P-and-O Ferries says the business is 'not viable in its current state' having made a 100-million pound year-on-year loss - and has made 800 staff redundant, effective immediately.