Members of the Rail, Maritime and Transport (RMT) union are due to take 14 days of action in a long-running row over the role of conductors.
The first walkout is due to start next week, threatening fresh disruption to Southern's services.
The company set a deadline of noon on Thursday for the union to accept its final offer.
The two sides are now meeting in London in a last-ditch attempt to solve the row.
The RMT said it will be tabling a set of new proposals that deal with all of the issues.
The union's General Secretary Mick Cash said he welcomed the talks and will meet Southern with "no pre-conditions and no arbitrary deadlines".
Angie Doll, Southern Passenger Services Director, said she hopes the talks will bring an end to the "unnecessary" dispute.
Months of industrial action by the RMT and high levels of staff sickness have hit Southern's services, which link London with Surrey, Sussex, Kent and Hampshire.
Strike dates announced by the RMT:
Southern has experienced strong criticism this week after a social media campaign backfired.
The company took out newspaper adverts and put posters at stations asking commuters to message the RMT on Twitter.
It has now ordered the posters to be taken down, but said press adverts would continue.
Fresh talks aimed at averting a series of strikes on the Southern rail network are being held.