Washington - U.S. diplomats and officials said they're bracing for at least three newspapers and WikiLeaks to publish today hundreds of thousands classified State Department cables that could drastically alter U.S. relations with top allies and reveal embarrassing secrets about U.S. foreign policy.

U.S. diplomats frantically have been reaching out to their counterparts around the world as intelligence officials pleaded with WikiLeaks and the newspapers, including The New York Times, the Guardian in London and Der Spiegel, a German newsweekly, to not publish information that could endanger lives and U.S. policy. Some of the documents are expected to reveal details about how some U.S. diplomats feel about top foreign leaders.

While this is the third time this year WikiLeaks has released a batch of documents related to U.S. foreign policy, officials told McClatchy that Sunday's expected release will be far more damaging than the first two combined.

The first batch dealt with Afghanistan and the second with Iraq. Both earlier releases largely gave details about what many thought the U.S. military was doing in those wars. This batch, however, is expected to include never-released private cables between diplomats.

Publicly, State Department spokesman P.J. Crowley warned that releasing the documents could put "lives and interests at risk." But privately, administration officials are far more concerned about what they contain and implications of releasing them.

NBC News reported Friday that some of the documents would reveal damaging details about U.S. efforts to renegotiate the START nuclear arms treaty with Russia and U.S. anti-terrorism efforts in Yemen.

Speculation is rampant in Washington about what's in the documents.

Germany's Der Spiegel briefly published a story on its website Saturday saying that the documents include 251,287 cables and 8,000 diplomatic directives, most of which date after 2004. About 9,000 documents are from the first two months of this year, the newspaper said.

About 6 percent of the documents were classified as secret, the newspaper said before taking down its story. The majority was unclassified, the newspaper said, but all were intended to remain confidential.

The newspaper said it would release all the documents at 4:30 p.m. EST today.