UPDATE 1-Caterpillar will take $100 mln Q1 charge

* $100 mln after-tax charge related to new law

* Not yet included in Q1 profit outlook

LOS ANGELES, March 24 (Reuters) - Caterpillar Inc (CAT.N) said on Wednesday it sees a roughly $100 million after-tax charge to earnings in the first quarter as a result of a new law that will lower the company's tax deductions.

The new rule, beginning in 2011, will increase the company's expected taxes under the newly-signed Patient Protection and Affordable Care Act.

Wall Street expects the world's largest maker of construction and mining equipment to post a net income of almost $280 million or 40 cents a share in the quarter ending March 2010, according to Thomson Reuters I/B/E/S.

The company said its 2010 profit outlook does not include the impact of the tax law change. Caterpillar in January forecast a 2010 earnings of $2.50 a share on sales of $35.6 billion to $40.5 billion . [ID:nN21182482]

Shares in Caterpillar were down a penny in after-hours trade, from a regular-session close of $62.06 on the New York Stock Exchange. (Reporting by Dana Ford; Editing by Bernard Orr)