Coastguard staff based in operations rooms have indicated their willingness to hold what would be their first strike in 186 years in a pay dispute.
Staff in the operations room coordinate rescue efforts
Some 90% of trade union members voting in a consultative ballot said they would be prepared to strike.
Unions say when the dispute began in May, a basic coastguard was being paid just 1p more than the minimum wage.
The government says it values the work of the UK's coastguards and negotiations over pay are continuing.
For months, coastguards have been working to rule, withdrawing non-essential 999 duties.
These include completing incident reports and end of month returns.
Up to 700 members of staff have participated in this industrial action.
Other duties affected include staffing a phone line which supplies information to the public and shipping companies, and the issuing of fishing vessel certificates.
Operations room staff, based in the UK's 19 co-ordination centres, were the only staff being asked about the possibility of strike action.
They co-ordinate search and rescue operations at sea by taking distress calls and deploying the relevant teams to those in need of help.
Following the "yes" vote, there could be a full strike ballot in January and a final decision on industrial action would then be taken.
In May, members of the Public and Commercial Services Union (PCS) working for the Maritime and Coastguard Agency (MCA) voted for industrial action short of a strike.
Following the result of the consultative ballot, PCS general secretary Mark Serwotka said: "The government and the MCA can be in no doubt about the feeling of injustice amongst people who deliver a vital emergency service and save lives.
"It is an absolute disgrace that you have coastguard watch assistants receiving a pay rise this October merely to comply with the increase in the national minimum wage."
The minimum wage for adults aged 22 and over is £5.52 an hour.