Koh wrote that the department had spoken with representatives from The New York Times, The Guardian and Der Spiegel newspapers about 250,000 documents the whistleblower organization provided to them for publication.
He described the distribution as the "illegal dissemination of classified documents" and said it would "place at risk the lives of countless individuals" -- criticisms that have been repeated by U.S. officials after past postings on the site.
The information blitz from WikiLeaks is expected to offer a glimpse into the worldwide communications of the State Department and its 297 embassies, consulates and missions through what commonly are referred to as "cables."
Koh wrote that releasing such documents could jeopardize relationships with allies, military actions and anti-terrorism operations.
WikiLeaks indicated last week that it was preparing to release a new batch of previously classified U.S. military documents.
"Next release is 7x the size of the Iraq War Logs," the group stated via Twitter Monday. "Intense pressure over it for months. Keep us strong."
CNN has not had advanced access to the documents, unlike some media organizations, because the company declined to sign a confidentiality agreement with WikiLeaks.
In October, WikiLeaks released nearly 400,000 U.S. military reports about operations in Iraq. In July, it released more than 70,000 reports from the war in Afghanistan.
In a letter to Julian Assange, founder of Wikileaks, the  said that releasing the documents would risk "countless" lives.

The  has urged Wikileaks not to publish new files because they will risk "countless" lives. In a letter to Julian Assange, founder of the whistle-blowing website, the Obama administration said that releasing the documents, rumoured to be seven times the size of the , would be in breach of U.S. law, and would result in "grave consequences." Assange replied by stating that the U.S. did not want to be held to account. 

It is thought that the files will include correspondence between U.S. diplomats around the world. ''Wikinews'' reported on Saturday that officials in Washington were contacting embassies around the world to warn diplomats of the leak. The letter to Assange came after he questioned who would be at risk from the publication of the documents. In the letter, , the , ordered Wikileaks to return the documents. "We will not engage in a negotiation regarding the further release or dissemination of illegally obtained US government classified materials," Koh wrote, adding that the documents could jeopardize  operations.

Analysts have said that the letter reflects the U.S. administration's concern over possible publication of the files, which may contain  opinions of other politicians, some of which may be candid and embarrassing. It is not known when the documents will be published, but Koh said in the letter that he had spoken to '''', '''', and '''' about the documents. Earlier this year, Wikileaks  detailing military actions in Afghanistan.