MasterCard is pulling the plug on payments to WikiLeaks, a move that will dry up another source of funds for the embattled document-sharing Web site, CNET has learned.

There are some things you can&39't buy with MasterCard.

"MasterCard is taking action to ensure that WikiLeaks can no longer accept MasterCard-branded products," a spokesman for MasterCard Worldwide said today.

That further limits the revenue sources for WikiLeaks, which has seen its finances systematically attacked in the last few days, as the Swiss authorities shut down a bank account used by editor Julian Assange, and PayPal permanently restricted the account used by the group. WikiLeaks has responded with an increasing number of fund-raising requests that urge supporters to "KEEP US STRONG."

Assuming that MasterCard blocks payments, the only easy way to donate electronically would be with a Visa credit card through a Web page hosted by Iceland-based DataCell.com. Representatives of Visa did not respond to requests for comment from CNET today. (WikiLeaks also solicits payments sent through the U.S. mail.)

MasterCard said it was cutting off payments because WikiLeaks is engaging in illegal activity. "MasterCard rules prohibit customers from directly or indirectly engaging in or facilitating any action that is illegal," spokesman Chris Monteiro said.

The move to cordon off WikiLeaks comes as a noose appears to be tightening around the neck of editor Julian Assange, who is the target of an arrest warrant issued today in the United Kingdom, according to a BBC report. He is expected to appear in a U.K. court tomorrow.

WikiLeaks previously was given the boot from its United States-based hosting services and domain name services. Sen. Joseph Lieberman of Connecticut said last Wednesday: "I call on any other company or organization that is hosting WikiLeaks to immediately terminate its relationship with them."

Since then, U.S. politicians have stepped up their criticism of the document-sharing site, which has posted only about 1,000 of 251,000 State Department dispatches it says it possesses and has shifted to the WikiLeaks.ch domain. "I think the man is a high-tech terrorist," Sen. Mitch McConnell (R-Ky.) said yesterday, referring to Assange. "He has done enormous damage to our country."

In addition, the incoming chairman of the House Homeland Security Committee wants WikiLeaks listed as a "terrorist" organization, which would prohibit U.S. banks from processing payments and make it a felony for anyone else to provide "material support or resources" to the group. CNET reported earlier today that some U.S. government employees are being blocked from visiting WikiLeaks' Web site and the myriad mirror sites that have sprouted in the last few days.