UPDATE 2-Mexican economic growth cools in first quarter

(Recasts, adds bullet points, detail and background)

* Mexico's economy grows 2.6 percent

* Growth slower than 4th quarter 2007 as US economy slides

* Holy Week holiday also crimps growth

* Retail and services grow while mining falls

MEXICO CITY, May 22 (Reuters) - Mexico's economy grew at a slower-than-expected 2.6 percent rate in the first quarter, the government said on Thursday, crimped by a slowdown in the United States and fewer working days because of a national holiday.

The government also said the economy expanded 0.51 percent in the first quarter compared with the fourth quarter of 2007 <MXGDPQ=ECI>.

Holy Week of the Easter season, a five-day holiday for many employees in Mexico, fell in March this year, trimming the number of working days in the first quarter compared to a year ago when the holiday was in April.

Discounting the effect of that holiday, growth in the quarter <MXGDPY=ECI> would have been 3.7 percent year over year, the government said in a statement.