Rail passengers in Portsmouth face further disruption after it was announced that a £100m signalling project will overrun for a second time.
Network rail has apologised for extension to signalling work
A limited service was introduced in the Hampshire city at the start of February after more than a month without trains.
Earlier this month Network Rail announced its project would overrun by six weeks until 18 March.
Now the company is unable to confirm when the signalling overhaul will be completed.
In a statement, Network Rail blamed the delay on "technical issues" that need resolving with Siemens, the company supplying the new signalling system.
David Pape, route director for Network Rail, said: "We apologise to passengers in the Portsmouth area for disruption and inconvenience this will cause.
"We appreciate they have already been patient, but we are asking for them to bear with us while we get the delivery of the project exactly right.
"We are disappointed for all our customers, and we will be doing everything we can to finish this work... as soon as possible."
Christian Roth, managing director of Siemens Transportation Systems also apologised, adding: "Our efforts continue to be focused on the delivery of a robust and reliable railway for the future."
South West Trains (SWT), which is operating a reduced service of two trains an hour to Portsmouth Harbour, said it shared passengers' frustration and was "pressurising Network Rail to complete the work as quickly as it can".
Scheduled engineering work for 15 and 16 March has been cancelled but work on 17 and 18 March will go ahead.
Extra work will be carried out from 31 March to 2 April.