UPDATE 2-GM IPO won't happen before 4th qtr -US Treasury

* U.S. Treasury says GM will decide timing

* Treasury to retain right on whether to participate

* GM to pick underwriters to be approved by Treasury

* GM says a number of factors to influence IPO timing (Adds Treasury will determine fees, GM comment)

By David Lawder

WASHINGTON, June 10 (Reuters) - A General Motors Co [GM.UL] initial public offering will not occur before the fourth quarter this year, and the timing will be decided by the company based on market conditions, the Obama administration said on Thursday.

The U.S. Treasury, which owns nearly 61 percent of the automaker's common shares after providing $50 billion in bankruptcy and bailout financing, said GM is taking charge of the preparation for a stock sale but the government would retain the right to decide whether to participate and at what level.

"The initial public offering is expected to include the sale of shares by Treasury, other shareholders who wish to participate and GM," the Treasury said.

GM said in a statement on Thursday that there was a "a lot of anticipation and speculation" relative to an IPO.

"As we have previously said, there are a number of factors that will influence the timing, including the state of the economy, capital market conditions, state of the auto business, GM's performance and others," GM said.

Chief Executive Ed Whitacre has said that an IPO was a real possibility later this year or in 2011.

GM Chief Financial Officer Chris Liddell last month said the company had not committed to an IPO timetable and there was still a lot of work to be done.

Treasury officials said the offering's overall size and split between primary and secondary shares would be determined at a later date. GM would select the lead underwriters but Treasury would approve them and determine their fees.

The Treasury last month hired Lazard Ltd (LAZ.N) as its adviser in a GM GM.UL offering that would return the automaker to public ownership after emerging from a government-sponsored bankruptcy last year.

Lazard will earn $500,000 per month until an IPO is completed under its 18-month contract with Treasury.

In addition to the U.S. Treasury, the United Auto Workers-aligned health care trust, the Canadian government, and old GM, now known as Motors Liquidation Company, hold significant stakes in GM equity.

In May, GM reported a $865 million net profit in the first quarter, surprising Wall Street, and said it was on track for its first full-year profit since 2004.

The Treasury said GM will prepare a registration statement, a prospectus and other documents, work with the Securities and Exchange Commission, and meet with potential investors.

"GM must determine that it is, in all relevant aspects, ready to become a public company. For those reasons, it is critical that the process of preparing for a potential IPO be managed by GM," the Treasury said. (Additional reporting by Soyoung Kim in Detroit; Editing by Leslie Adler)