UPDATE 1-Argentina's March primary surplus up 5.8 pct

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BUENOS AIRES, April 24 (Reuters) - Argentina's primary budget surplus, closely watched by investors as a creditworthiness gauge, rose a slightly lower-than-expected 5.8 percent in March compared to a year earlier, the government said on Tuesday.

The primary budget surplus in March was 1.49 billion pesos ($476 million) versus $1.4 billion pesos in March 2006, Economy Minister Felisa Miceli told reporters.

Miceli said the accumulated surplus for the first quarter reached $5.09 billion pesos, representing a 3.6 percent rise over the same period last year.

"The primary budget surplus in the first quarter is 25 percent higher than what was forecast in the government's budget," she said.

The government has forecast a primary budget surplus this year of 21.82 billion pesos.

The primary budget represents the amount of excess government revenue before it makes interest payments.

The March figure was slightly lower than the median forecast of 1.503 billion pesos given in last month's central bank survey BCRA30.

Argentina's tax revenue rose 33.6 percent in March from a year earlier due to an overall increase in activity in Latin America's No.3 economy.

Argentina registered a primary budget surplus of 23.16 billion pesos in 2006, the equivalent of 3.6 percent of the gross domestic product.

The Argentine economy has grown by nearly 9 percent over the last four years after a deep crisis in 2001-2002.

($1= 3.1175 Argentine pesos)