WikiLeaks was on the defensive on several fronts Wednesday, scrambling to remain on the Internet and post more U.S. diplomatic documents while its fugitive founder Julian Assange was targeted by a European arrest warrant on Swedish rape charges.

Amazon.com Inc. prevented WikiLeaks from using the U.S. company's computers to distribute embarrassing State Department communications and other documents, WikiLeaks said Wednesday. The WikiLeaks site was unavailable for several hours before it moved back to servers owned by its previous Swedish host, Bahnhof, which are housed in a protective Cold-War era bunker.

At the same time, Swedish officials intensified legal pressure on Assange by asking European police to arrest him on rape allegations that have shadowed him for weeks. Swedish Director of Public Prosecution Marianne Ny said that the European arrest warrant had been issued for Assange in connection with the allegations filed against him in that country.

Amazon's move to kick WikiLeaks off its servers came after congressional staff called the company Tuesday to inquire about its relationship with WikiLeaks, Sen. Joe Lieberman, the Connecticut independent, said Wednesday.

"The company's decision to cut off Wikileaks now is the right decision and should set the standard for other companies Wikileaks is using to distribute its illegally seized material," Lieberman said in a statement. He added that he would have further questions for Amazon about its dealings with WikiLeaks.

The White House said Wednesday it was taking new steps to protect government secrets after WikiLeaks release of thousands of sensitive U.S. diplomatic cables. Officials said national security adviser Tom Donilon has appointed a senior aide to identify and develop reforms needed in light of the document dump.

The White House also spurned a call from Assange for Secretary of State Hillary Rodham Clinton to step down if she had any role in directing U.S. diplomats' spying on other foreign leaders. "Mr. Assange's suggestion is ridiculous and absurd, and why anyone would find his opinion here relevant is baffling," said spokesman Tommy Vietor, adding Clinton was doing an "extraordinary" job. The White House says U.S. diplomats do not engage in spying.

Clinton was in Astana, Kazakhstan, enduring repeated comments about the WikiLeaks disclosures as she met with foreign officials at a conference of international leaders.

Among those she met with was Italian Prime Minister Silvio Berlusconi, who had been described in newly released U.S. diplomatic cables as "feckless" and a party animal.

"We have no better friend, we have no one who supports the American policies as consistently as Prime Minister Berlusconi has, starting in the Clinton administration, through the Bush administration, and now the Obama administration," she said during a summit of the Organization for Security and Cooperation in Europe.

A senior State Department official said that in her meeting with Berlusconi, the Italian leader raised the WikiLeaks matter, saying the publicity it had generated in Italy was a political problem for him. The official, who spoke on condition of anonymity in order to describe a private conversation, said Clinton expressed regret for the leak, calling it an illegal act.

The WikiLeaks matter was discussed in virtually all of Clinton's private one-on-one meetings with European leaders and foreign ministers during the summit meeting Wednesday.

"I have certainly raised the issue of the leaks in order to assure our colleagues that it will not in any way interfere with American diplomacy or our commitment to continuing important work that is ongoing," Clinton said.

Assange's call for Clinton's resignation came in an online interview Tuesday with Time magazine from an undisclosed location. Assange said Clinton should step down "if it can be shown that she was responsible for ordering U.S. diplomatic figures to engage in espionage in the United Nations" in violation of international agreements.

State Department officials have acknowledged that secret instructions to American diplomats to gather sensitive personal information about foreign leaders originated from the U.S. intelligence community. But diplomats were not required to spy, the officials said.

Assange remained a fugitive Wednesday, shadowed by the Europe-wide arrest warrant. A German security official, speaking on condition of anonymity because no authorization was given to discuss the legal steps, confirmed that a warrant for Assange had been issued in that country.

Assange's London-based lawyer, Mark Stephens, complained his client had yet to receive formal notice of the allegations he faces — something Stephens described as a legal requirement under European law. The lawyer added that Assange had repeatedly offered to answer questions about the investigation, to no avail.

The 39-year-old Australian computer hacker has been out of public sight since a Nov. 5 news conference in Geneva. He has spoken publicly only through online interviews, while a statement from his lawyer said the Australian was being persecuted by Swedish officials seeking his arrest on allegations of rape, sexual molestation and unlawful coercion.

The exact nature of the allegations facing Assange aren't completely clear. Stephens has in the past described them as a part of "a post-facto dispute over consensual, but unprotected sex." Even Swedish prosecutors have disagreed about whether to label the most serious charge as rape.

Formal charges have not been filed, but a detention order issued at Ny's request on Nov. 18 remains in force pending an appeal by Assange. The case is now before Sweden's Supreme Court.

Meanwhile, Assange's secret-spilling group is still in the process of disclosing hundreds of classified State Department cables, which have revealed requests for U.S. diplomats to gather personal information on their foreign counterparts, highlighted Western concerns that Islamist militants might get access to Pakistan's nuclear material and American skepticism that Islamabad will sever ties to Taliban factions fighting in Afghanistan.