The delivery date for the final phase of the International Slavery Museum, originally 2010, has been left open ended, as National Museums Liverpool (NML) seeks to raise £5m to complete it.

The former Dock Traffic Office, which NML bought for £1.8m, is to be converted into a research and resource centre, linking the museum with offices, more exhibition space and educational facilities.

NML director David Fleming said he did not expect the recession to damage NML's chances of raising £5m and that work would begin as soon as a "decent proportion" of the funding had been raised.

If that happened in this financial year, he said the museum might open in 2010.