A BART shutdown for Tuesday morning was averted after both sides agreed to keep talking into the wee hours.

Federal mediator George Cohen made the announcement around 1 a.m. and said both sides had made 'substantial progress' but declined to elaborate. It was unclear whether another strike would be threatened for Wednesday or later.

'We apologize (that) the Bay Area continues to have to wait until the middle of the night to find out if union leadership will allow the trains to run each morning,' BART said in a statement early Tuesday. 'We hope we can get this situation resolved quickly so the uncertainty can come to an end.'

Management and BART's two large labor unions faced an 11:59 p.m. .