The RMT wants a 5% pay rise and no compulsory redundancies
Millions of commuters and visitors to London face travel chaos after talks aimed at averting a two-day strike by Tube workers broke down.
The announcement was made after 10-hour talks failed to produce a breakthrough in the dispute, over jobs and pay.
The walkout, which is expected to affect the entire Tube network, was triggered after a Rail, Maritime and Transport Union ballot last month.
The strike is due to begin at 1859 BST on Tuesday and end 48 hours later.
Normal services are expected to resume on Friday morning.
Their (the RMT's) attitude is a slap in the face to all hardworking Londoners and businesses struggling through a deep recession
Peter Hendy, TfL
Transport for London (TfL) described the RMT's decision to call for strike action as "outrageous", following London's Underground's offer on Friday.
It offered staff a four-year deal of 1.5% this year and then the inflation rate plus 0.5%; or a two-year deal of 1% now and inflation plus 0.5% in year two.
But the RMT wants a 5% pay rise and a promise of no compulsory redundancies.
TfL's transport commissioner Peter Hendy said: "The RMT's leadership has shown yet again that no matter how far an offer is made, they would rather strike than talk.
"Their attitude is a slap in the face to all hard-working Londoners and businesses struggling through a deep recession."
Docklands Light Railway and London Overground services will operate as normal.
Transport for London (TfL) has said there will be 100 extra buses, extra river services, taxi-sharing at major railway stations, escorted commuter cycle rides into central London, additional cycle parking and a free river shuttle service to help travellers get around London.
"Pay as you go" Oyster cardholders will be able to use National Rail services in London on Wednesday and Thursday.
I urge the RMT to stop disrupting the lives of millions of people
TfL staff will also be on hand across the bus network and at Tube stations to offer travel advice and distribute walking maps in central London.
London mayor Boris Johnson criticised RMT leaders, calling the strike a "ludicrous and unnecessary disruption".
"I urge them to stop disrupting the lives of millions of people, put the needs of their members and of Londoners first, get back to the table and reach an agreement," he said.
RMT general secretary Bob Crow said the union had made every effort during the talks to reach a deal with London Underground.
He said: "Not only could the management side not reach an agreement on the kind of deal needed to end this dispute, they also found it difficult to stick to existing agreements on redundancies.
"The strike will now go ahead and we expect it to be solidly supported."
The union balloted up to 10,000 of its members, including drivers, station staff and maintenance workers.
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