Ritchie Capital chief executive Thane Ritchie had sought to buy the Sun-Times Media Group last year. He said he would make an offer for Newsweek personally, and not on behalf of his firm.
Andrew Nikou, managing partner at OpenGate Capital, which bought TV Guide in 2008 for $1, said his firm is also interested in the Washington Post-owned magazine.
Newsweek has lost $44m since 2007, according to financial documents distributed to prospective buyers.
Washington Post Co stock has risen 5.9 percent this year, although it fell $4.27 to touch $465.73 at the NYSE. The publisher said it is accepting expressions of interest from potential buyers until 5 pm on 2 June.