Diversified manufacturer 3M Co issued a cautious initial outlook for 2010 on Tuesday, saying tight credit market conditions and other headwinds would make any broad economic recovery patchy and slow.

The company also updated its 2009 earnings estimate, warning that it would fall just short of Wall Street's estimates, sending its shares down about 1.2 percent.

We all know we're going through some transitions in the economy and forecasting is very, very difficult, George Buckley, the company's president, chief executive and chairman, told investors at the company's year-end outlook conference.

2009 was a very interesting year. But 2010 is going to be even more interesting, he said.

The coming year will likely be marked by real market share transfers as weaker companies, unable to tap credit markets as before, fall by the wayside, he said.

As the economy does come back, I think it's going to be hard for people to fund their growth, he said. So I think the strong are going to get stronger and the weak won't.

3M said it now expects full-year 2009 earnings excluding items of between $4.50 and $4.55 per share -- below analyst estimates of $4.57, according to Thomson Reuters I/B/E/S.

For 2010, 3M expects earnings in the range of $4.85 per share to $5.00 per share on sales of $24.5 billion to $25.5 billion, topping analyst estimates of $24.46 billion.

Analysts' earnings estimates of $4.94 per share, according to Thomson Reuters I/B/E/S, fall in the upper end of the company's projected range.

3M shares were down about 1.2 percent at $76.98 in mid-morning trading on the New York Stock Exchange.

(Editing by Maureen Bavdek, Dave Zimmerman and Ted Kerr)