UPDATE 2-Chile 1st-half fiscal surplus 4.0 pct of GDP

(Updates with tax, copper revenue data, quote)

SANTIAGO, July 30 (Reuters) - Chile's public sector posted a fiscal surplus in the first half of 2008 of 4.0 percent of gross domestic product, the government said on Wednesday, and a second-quarter surplus of 1.0 percent of GDP.

Government budget director Alberto Arenas said budgeted central government revenues fell 19.4 percent during the second quarter in real terms compared to the same period in 2007.

In the first quarter the fiscal surplus was a record 3.0 percent of GDP, and the government has forecast it will hit 6.7 percent of GDP for the full year.

"The accumulated surplus during the first half is in line with the 6.7 percent of GDP forecast for the year," Arenas told reporters.

Tax revenue from the private mining sector fell 31.9 percent in the first half, while copper revenue fell 19.4 percent during the period. Copper is the mainstay of the Chilean economy, accounting for more than half of exports of the world's No. 1 producer of the metal.

Chile's fiscal surplus in 2007 was worth a record 8.8 percent of GDP, according to revised figures.

The government this month lowered its forecast for 2008 GDP growth to 4.2 percent from a previous estimate of 5.3 percent, amid higher inflation and lower output. (Reporting by Rodrigo Martinez; Writing by Simon Gardner; Editing by James Dalgleish)