Dockworkers at the UK’s Port of Liverpool rejected their employer’s latest pay offer, setting the stage for a two-week strike at the nation’s fourth-biggest gateway for global trade in a widening labor dispute that threatens more strains on the British economy.

The unanimous vote took place at a stop work meeting late Monday, with port operatives and the engineering department turning down Peel Ports Ltd.’s proposal of a 7% wage increase and a one-time payment of £750 ($875). Organizers estimated the turnout at about 500 members and pledged to picket 24 hours a day starting Sept. 20.

The UK’s supply chains are growing increasingly fragile heading into the peak season for pre-holiday shipping and a winter of soaring heating bills. Liverpool’s dockworkers are trying to get a pay increase closer to the rate of inflation, which has soared above 10%.

In a separate vote, workers at Felixstowe rejected a pay deal imposed by management, paving the way for a new round of industrial action and disruption at Britain’s busiest container port. That walkout is set to occur Sept. 27 to Oct. 5. 

If the two ports’ strikes overlap, the stoppages will temporarily staunch the flow of more than half of the UK’s container exports and imports.

In Felixstowe, some 82% of votes cast in a ballot of Unite union members opposed a 7% raise and £500 bonus to be implemented by the UK arm of CK Hutchison Holdings Ltd., Bobby Morton, the labor group’s national officer, said by phone Monday.

In August, Felixstowe was hit by eight days of walkouts involving almost 2,000 staff, a shutdown that forced shipping lines to reroute cargo and alter delivery schedules. Unite, which is pressing for a raise of at least 10%, said it expects to announce new strike dates Tuesday.