UPDATE 1-Argentina July primary surplus 4.02 bln pesos-president

(Adds details)

BUENOS AIRES, Aug 19 (Reuters) - Argentina's primary budget surplus widened by 56 percent to 4.02 billion pesos ($1.31 billion) in July, President Cristina Fernandez said on Tuesday.

Fernandez spoke during a public appearance announcing a new public works project in the province of Buenos Aires, but did not cite a comparative figure or provide details.

She also announced Argentina's trade surplus in July was $1 billion.

A central bank poll of analysts forecast a primary surplus in July at a median of $2.9 billion pesos BCRA30.

($1 = 3.065 Argentine pesos) (Reporting by Walter Bianchi; Writing by Kevin Gray; Editing by Diane Craft)