The Australian, who was spending his second full day on bail, vowed the whistle-blowing site would carry on releasing controversial leaked US diplomatic cables as he insisted his life was under threat.
Bank of America, the largest US bank, halted all transactions for WikiLeaks, joining other institutions that have refused to process payments for the website since it started to publish the documents last month.
"Bank of America joins in the actions previously announced by MasterCard, PayPal, Visa Europe and others and will not process transactions of any type that we have reason to believe are intended for WikiLeaks," it said in a statement.
"This decision is based upon our reasonable belief that WikiLeaks may be engaged in activities that are, among other things, inconsistent with our internal policies for processing payments."
Assange said there was a fiscal witch-hunt against the website.
"It's a new type of business McCarthyism in the US to deprive this organisation of the funds that it needs to survive, to deprive me personally of the funds that my lawyers need to protect me against extradition to the US or to Sweden," Assange told AFP.
The term, referring to allegations of treason or subversion without proof, was coined to describe the anti-communist pursuits of former US senator Joseph McCarthy from the late 1940s to the 1950s.