Vikram Pandit, in a conference call to employees Friday, began a counterattack on dissident investors, saying they were engaging "fear mongering" and denounced chatter "fueled by competitors" that has resulted in Citigroup's stock price tumbling 60 percent this week to a 16-year low, The Wall Street Journal reported.

Citigroup, which has already received $25 billion from the government's Troubled Asset Relief Program, is under pressure to sell its Smith Barney brokerage unit or other pieces of the company to raise cash and stop its stock slide.

But Pandit declared he has "no desire" to sell the unit, the newspaper said. Instead, the company's board is hoping to gain a public expression of confidence from U.S. Treasury Secretary Henry Paulson that would serve to ease its investors' concerns.

Citigroup's executives, however, haven't ruled out a possible sale or breakup of the company if they determine there is no alternative, people familiar with the situation told the Journal.