SAN JOSE, March 16 (Reuters) - Costa Rica's economy will grow 4 percent in 2015, helped by higher levels of public investment, Finance Minister Helio Fallas said on Monday.

"Higher public and private investment is having a multiplying effect on the economy," Fallas told journalists.

Costa Rica's Central Bank, which expects economic growth of 3.4 percent for the year, lowered its main interest rate to 4.75 percent in February to take advantage of a steep decline in oil prices.

The country's economy grew 3.5 percent in 2014.

(Reporting by Enrique Pretel; Editing by Ken Wills)