Lula, an outspoken populist with an eye on a third term after he hands over power Jan. 1 to Workers Party protege Dilma Rousseff, indicated he saw nothing wrong in Assange's conduct.
Assange surrendered to U.K. law enforcement authorities Dec. 7 after Sweden released an international arrest warrant for him to face sexual assault charges. Media reports claimed the case against Assange was previously dropped by Swedish prosecutors but was revived when WikiLeaks began publishing U.S. diplomatic cables.
Sweden denies the arrest warrant is politically motivated.
Lula, a former trade union leader, said at a gathering in Brasilia that Assange, through his publication of about 250,000 U.S. diplomatic documents, appeared to have done less harm than the classified documents' authors, MercoPress reported.
"I'm surprised they arrested the man and I didn't see any protest, not a word in defense of freedom of expression or freedom of the press," Lula said. "The guy was just posting what he read."
Supporters of Assange and WikiLeaks have inundated the Internet with mirror sites that continue to reproduce leaked diplomatic message even as WikiLeaks struggles with domain hosts and access to payment systems that allow it to receipt supporters' funds.
Meanwhile, details of the cables, published in The New York Times, The Guardian newspaper in Britain and Spain's El Pais, showed U.S. government officials tried to obtain Brazil's help in isolating Venezuelan President Hugo Chavez.
The cables also showed U.S. diplomats discussing members of the Lula administration that were considered anti-American.
Responding to the leaks, Lula said that WikiLeaks "exposed a diplomacy that seemed
to be untouchable" and yet faced problems after the disclosures. Lula said U.S. President Barack Obama had cause to be "very worried."
Lula said the leaks carried a lesson for Brazilian diplomats as well and warned government officials to beware of what they put on record.
"I'm going to talk it over with Dilma about our diplomats and what messages they send." His advice to Brazilian diplomats, Lula said, was that "if you don't have anything to write, don't write silliness."
In his two terms in office, Lula pursued what he described as an independent foreign policy, backing Iran's right to independent nuclear energy program and keeping a low key response to Latin American and Western pronouncements against populist governments, especially Chavez in Venezuela.