(Adds finmin comment on growth in Q4, 2015)
By Nelson Bocanegra and Carlos Vargas
BOGOTA, Dec 15 (Reuters) - Colombia's economy grew 4.2 percent in the third quarter from a year earlier, the government's statistics agency said on Monday, with construction offsetting a flagging industrial sector and declining oil income.
The increase was the smallest since the first quarter of 2013 and was just below the 4.3 percent median forecast of analysts in a Reuters survey. The data will probably reinforce expectations that the central bank will hold the benchmark interest rate when its board meets on Friday.
The South American nation's gross domestic product grew 0.6 percent from the second quarter, statistics agency DANE said, slower than the analysts' 0.9 percent forecast.
The finance ministry said the result supported its aim for 4.7 percent growth in all of 2014 after expansion of 6.5 percent in the first quarter and 4.3 percent in the second.
Finance Minister Mauricio Cardenas said fourth-quarter growth was likely to be stronger than in the third, with recovery in some weaker sectors.
"I would dare to anticipate that with manufacturing, which is already showing a pickup so far this year, and oil production, that the fourth quarter will be better," he said.
However, the government is likely to cut its official growth forecast for 2015 to about 4.5 percent from 4.8 percent, he said, due mainly to lower oil prices.
In the third quarter, the construction sector grew fastest, at 12.7 percent from a year earlier. Manufacturing shrank 0.3 percent, and the value of the oil and mining sector's output was down 1 percent.
The impact of the sharp drop in global oil prices, which have fallen around 40 percent since June, is likely to be felt even more in the fourth quarter.
Lower oil revenues have caused Colombia's currency to weaken to about 2,400 pesos to the dollar, its lowest value since 2006. Coal production from the world's fourth-biggest exporter of the fuel rose 2.4 percent in the quarter.
The central bank board's meeting on Friday will set the benchmark interest rate for the next month. The board has held the rate at 4.5 percent since late August. Twelve-month inflation has picked up, at 3.65 percent in November, but it is still inside the bank's 2 percent to 4 percent target range.
Banco de Bogota chief economist Camilo Perez told Reuters he believed the economy's continuing expansion would prompt the central bank to leave the benchmark interest rate unchanged well into next year. (Writing by Peter Murphy and Julia Symmes Cobb; Editing by Tom Brown and Lisa Von Ahn)