The results of a ballot on industrial action by London Underground workers over a three-year pay offer are to be announced later.
Thousands of Tube workers have voted to go on strike in a row over pay.
Members of the Rail Maritime and Transport (RMT) union are expected to vote in favour of strike action.
London Underground (LU) is locked in a dispute with the Rail Maritime and Transport (RMT) union which has rejected a three-year pay offer.
On Friday leaders of the rail union Aslef announced they were advising members to accept the pay offer.
Members of the RMT voted by 2,271 to 705 in favour of taking industrial action, with the turnout in the ballot being almost 50%.
The three-year deal involves a 4% pay rise from last April followed by annual increases of inflation.
The three-year deal was for an initial 4% pay rise from last April, followed by annual increases based on inflation.
'Constant attempts'
Leaders of the drivers' union, Aslef, have decided to recommend acceptance of the offer.
This also includes at least 0.5% with extra cash bonuses for achieving customer satisfaction targets.
An LU spokesman said: "London Underground has made a very fair pay offer to all trade unions. It is a three-year deal with an above inflation pay rise in each year, plus a cash bonus for all staff if customer satisfaction targets are met or exceeded."
But RMT general secretary Bob Crow said: "We have made constant attempts to get London Underground to negotiate seriously and to pay our members the rise that was due last April, but management continue to insist on withholding it.
"There is widespread anger among our members over LU's refusal to give them the 10 months' back-pay they are owed."
The Transport Salaried Staffs Association has already accepted the deal.
The Transport Salaried Staffs Association has already accepted the deal.
Aslef's announcement that it was recommending acceptance of the pay offer was welcomed by LU and London's mayor Ken Livingstone.
The RMT union executive is meeting in London to consider the result of the ballot and decide whether to name strike dates.
