Jamaican-born nurse/entrepreneur Mary Seacole is best known for her care and hospitality for British soldiers during the Crimean war.
The statue – which will face the Houses of Parliament across the Thames – has been designed by Martin Jennings.
The appeal's chairman Lord Soley wrote to supporters this week: "I wish to thank all those organisers and contributors to the Last Lap campaign. It has been a great success and means that there is just £27,200 outstanding to meet the cost of work carried out by the foundry and the sculptor Martin Jennings. I am confident that we will now raise that money over the next few months and see the statue completed.
"Despite this success we now have to raise an additional £180,000 to meet unexpected installation costs. As a result we have had to delay the unveiling and we will agree a new date in the New Year.
He continued: "As a result of these most recent developments I have also been involved in discussions with the Army about combining the memorial with a memorial dedicated to nurses in conflict. I will be discussing this concept with Guy's and St Thomas' NHS Foundation Trust.
"The Army is enthusiastic about this proposal. Importantly this opens up the possibility of access to other sources of funding."
Lord Soley added: "I am not prepared to see the completed statue, to which so many of our supporters have contributed, lying in the foundry ready but not in place."
Critics of the memorial argue that Seacole – though worthy of recognition – had no association with St Thomas' Hospital or formal hospital nursing and some claim that it is inappropriate to place her statue in a setting so closely linked to Florence Nightingale.
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