Facebook may take away a disputed page on Facebook from both Merck in Germany and Merck in the US, if the two companies do not come to an agreement, a person familiar with the situation has said.

The page Facebook.com/Merck was not accessible by late Monday, and the Merck US page had moved to another location on the social network.

Germany's Merck KGaA threatened legal action after it said it lost its Facebook page apparently to rival Merck & Co. in the U.S.

Facebook on Monday apologised for what it described as an "administrative error".

The dispute reflects the growing importance businesses attach to having branded pages on Facebook and other social networks.

In a filing last week before the Supreme Court of the State of New York, Merck Germany said that as Facebook is an important marketing device, the page is of great value, and its misappropriation is causing harm to the company.

By about Oct. 11 this year, it said it found that it had lost administrative rights to the page which now had content that appeared to be "created by, and is related to" Merck & Co. in the U.S.

"The transfer of the vanity URL Facebook.com/Merck from Merck KGaA to Merck & Co. was due to an administrative error," Facebook said in a statement. "We apologize for any inconvenience this may have caused," it added.

A vanity URL (uniform resource locator) on Facebook and other social networks is a distinct web address that reflects a user name.

Facebook will however make Facebook.com/Merck unavailable unless and until the two companies mutually agree that one can use it, said the person who requested not to be named.

Facebook has contacted Merck KGaA and Merck & Co. to explain the situation and inform them of Facebook's intention to remove the vanity URL. Each company will however be welcome to set up a new username and vanity URL reflecting their particular company, or is welcome to maintain an official page on Facebook without a vanity URL, the source said.

Merck & Co. and Merck KGaA were not immediately available for comment. Merck & Co. said on its new page that earlier on Monday, "Facebook announced plans to decommission our vanity URL due to an administrative error on Facebook's part".

"We want to assure you that our Facebook page will remain active and continue to serve as a helpful resource for information on health and well-being," Merck U.S. added. On Sept. 16, it carried a post welcoming users to "Merck's official Facebook page!"

Merck & Co. was formed in 1891, but became an independent US company after the First World War.