Bruno Senna could bring a new title sponsor to Williams.
A spokeswoman for the beleaguered British team has confirmed to the Telegraph that American telecommunications multinational AT and T is no longer its title sponsor.
"We have reached the conclusion of our partnership, the contract expired on December 31 by mutual agreement," she said.
The Reuters news agency said Williams, ninth in the constructors' championship last season, is in "advanced negotiations" over title sponsorship with another telecommunications company.
Finland's Turun Sanomat said one candidate is Embratel, a Rio de Janeiro based company that backs Brazilian driver candidate Senna.
A team source told Reuters that the ATT deal, reported to be worth just $7 million to Williams in 2011, was not "sustainable".
The Williams spokeswoman, meanwhile, would not comment on reported links between the Oxfordshire based team and touted major sponsor Qatar National Bank (QNB).
QNB is already affiliated with the team through Williams' partnership with the Qatar Science and Technology Park.
The bank is also in partnership with Qatar Telecom (Qtel).