(Adds Rio Tinto comment in paragraph 4-5) SANTIAGO, April 16...

(Adds Rio Tinto comment in paragraph 4-5)

SANTIAGO, April 16 (Reuters) - Chile's government needs to quickly approve a proposal to streamline permitting for the mining industry to unlock and promote investment in the world's top copper-producing country, a top executives said on Tuesday.

"In Chile it is urgent to improve the permit system to allow companies to approve large investment projects in a timely manner," BHP President Americas Brandon Craig said on a panel at the World Copper Conference being held in Santiago.

"This not only applies to new projects, but also to permits needed to optimize current operations," he added. BHP is a top copper producer and its flagship Escondida mine in Chile is the world's largest copper mine.

Rio Tinto, which has a 30% stake in Escondida and partnered with state-run Codelco for copper exploration, agreed that more streamlining is needed to boost investment.

"I would like to invest more in Chile, but I need help," said Bold Baatar, head of Rio Tinto's copper business. "The more we can streamline the permitting process (in Chile) ... I think that would be helpful."

Mining companies and industry groups have complained about the extensive permitting process in Chile. In January, the government presented legal reforms to streamline permitting for investments, which can currently reach up to 500 requests from various authorities.

The reforms still must be approved by Congress, where the government has faced strong opposition. The government was able to pass a mining tax reform last year, but a major industry request during the debate was to streamline permitting and reduce start-up times for multi-million dollar copper projects, which is Chile's largest export.

"I hope these reforms are approved quickly so that the industry can unlock large mining investments," Craig said.