US secretary of state Hilary Clinton has pledged US$15m (£9.9m, €12m) towards efforts to preserve Auschwitz-Birkenau concentration camp in Poland.

A funding appeal was launched by the Auschwitz-Birkenau Museum and Memorial last year after it was revealed that at least €120m (£99.4m, US$150m) was required for the long-term conservation of the site.

In a speech at the Schindler Factory Museum in Krakow on 3 July, Clinton revealed the US would contribute funding over a five-year period towards conservation efforts, subject to the approval of Congress.

Set in nearly 200 hectares (494 acres) of land, the concentration camp is one of Nazi Germany's most infamous and includes 300 ruins, more than 300 buildings and a collection of documents and other items.

Admission to the museum and memorial is currently free, with more than 1.3 million visitors during 2009. The museum's permanent exhibition first opened in 1955, including photographs, documents and historic artefacts.

A spokesperson for the US Department of State said: "The United States strongly encourages other nations who have not already done so to follow suit and to contribute to the Auschwitz-Birkenau fund to preserve the site for future generations.

"The preservation and continuation of Auschwitz-Birkenau is essential so that future generations can visit and understand how the world can never again allow a place of such hatred and persecution to exist."