The Treasury Department said Friday that it plans to sell an additional 1.5 billion shares of Citigroup Inc., or about one-third of its remaining 5.1 billion common shares in the company.

A Treasury spokesman said the sale would begin "any time" after Friday's announcement. The sale is to end Sept. 30, even if not all of the 1.5 billion shares have been sold, due to the blackout period required for Citi's third-quarter earnings release.

The government has already unloaded 2.6 billion Citi shares in two tranches for about $10.5 billion in gross proceeds. During the 2008 financial crisis, the government got 7.7 billion shares in the company in the course of bailing it out.

The sale of this third tranche of Citi stock is being conducted by Morgan Stanley, which also handled the previous two phases of the trading program.

Subscribe Now

Access to authoritative analysis and perspective and our data-driven report series.

14-Day Free Trial

No credit card required. Complete access to articles, breaking news and industry data.