Talks aimed at averting another strike by London Underground workers will resume today, just hours before the latest walkout is due to start.
Leaders of the RMT and TSSA unions and LU managers spent all day at the conciliation service Acas yesterday to try to resolve a row over Tube ticket office closures.
The talks were adjourned until today, giving the two sides one last chance to avoid another crippling stoppage on the Tube.
Workers are due to strike for 48 hours from 9pm tonight in protest at controversial plans to close all Tube ticket offices, with the loss of 950 jobs.
A 48-hour stoppage last week caused travel chaos in the capital.
The Federation of Small Businesses (FSB) estimated that last week's action cost small firms in the capital £600 million in lost working hours, business and productivity.
The FSB said London businesses affected by the strikes lost an average of £1,297 each, according to a snap poll of over 600 of its members.
In London, 58% of members were negatively affected by the shut down with most saying cancelled meetings, staff absences and difficulty transporting goods and services were the main problems.
Many businesses said loss of demand for goods and fewer customers also caused problems.
FSB members in the south east were also negatively affected, with cancelled meetings being the main problem for almost two thirds of firms in the region.
FSB chairman John Allan said: "The capital is bracing itself for more disruption this week as another round of strikes is due to take place.
"With small firms estimating a cost of £600 million across the capital, they are rightly concerned about the impact a second round would have.
" As the ripples could be felt outside London, the economy just can't afford that right now. We would encourage businesses to look at contingency plans for the next planned action.
"Ultimately, those businesses where staff and customers rely on the Tube could be put at a further disadvantage."
LU warned passengers that Tube services will again be disrupted this week if the strike goes ahead.
Managing Director, Mike Brown said: "I urge the leaders of the RMT and TSSA to work with us to help shape the future of the Tube.
"Talks continue at Acas to try to resolve this dispute. All that another unnecessary strike will achieve is to lose those who take part another two days' pay.
"Should the strike go ahead, we'll do all we can to keep customers informed and ensure we keep London moving and open for business."
LU said it will keep as many stations open and run as many trains as possible if there is another strike, but warned that services will be affected from 9.30pm tonight.
Customers were asked to try to complete journeys as early as possible and to top up Oyster cards in advance of the industrial action starting.
A statement said: "There could be disruption to journeys on Wednesday and Thursday, resulting in Tube services starting later and finishing earlier than normal.
"If strike action does take place and where we can operate services, trains will run from around 7am and they are expected to conclude around 11pm, with no service beyond that.
"However, customers are advised that the last services from central London may depart significantly earlier than this, at around 9.30pm.
"Buses and other modes of transport will also be very busy."