ASUNCION (Reuters) - Paraguay's economy is on track to grow a faster-than-expected 4% this year, President Santiago Pena told Reuters on Wednesday, a bullish forecast above official estimates that comes despite depressed prices for its top export, soy.

Pena, 45, said growth would beat the current central bank estimate of 3.8%, already one of the region's highest.

"We are confident that we are going to have growth above 4%," Pena said from the presidential residence in capital Asuncion, citing strong investment and aid to help farmers ship exports.

That support will include deepening waterways needed for grains shipments that have been affected by low river levels, he said.

As the economy booms, Pena said he expected ratings agencies such as S&P and Fitch to upgrade the country's sovereign debt rating early next year. Moody's hiked Paraguay's rating to investment grade in July, citing fiscal policy stability and state investments.

Paraguay is in advanced talks to join the Organization for Economic Co-operation and Development (OECD) by the end of his current term in 2028, added Pena, an economist who came into power a year ago with the conservative Colorado party.