Thousands of London Underground staff are to vote on strike action in a row over pay, their union has announced.
Talks over pay negotiations have broken down
The Rail, Maritime and Transport Union (RMT) said 6,500 would be balloted, including drivers and station staff.
The union said it had spent 10 months in "fruitless attempts" to hold meaningful negotiations, adding that a pay rise was due last April.
London Underground (LU) said its offer of a three-year above inflation pay rise was "very fair".
The offer would see a 4% rise for this financial year, and a rise at the rate of inflation plus 0.5% in each of the following two years.
"Rather than balloting for strike action, the RMT should be putting this very fair offer to their members," said an LU spokesman.
RMT general secretary Bob Crow said: "We have spent months trying to get London Underground to negotiate sensibly with us.
"We have now reached the end of the road.
"LU can avoid industrial action by paying the increase that is due to our members.
London Assembly member Geoff Pope urged both sides to immediately work together to resolve their differences.
"It's totally unacceptable that, once again, Londoners are facing a threat of further disruption to their daily travel," he said.
The last Tube-wide strike was in the summer of 2004 when RMT members took industrial action, again over pay.
The ballot will end in mid-February and any strikes could start at the end of next month.