MOSCOW (Reuters) - Russia's federal budget deficit amounted to 4.3 percent of GDP in the first half of 2016, Finance Minister Anton Siluanov said on Wednesday, underscoring the need for spending cutbacks.

"The deficit in the first half ... was 4.3 percent, significantly higher than we foresee for the year," Siluanov said.

He added that the relatively high deficit had been caused by a 12 percent decline in government revenues, primarily oil and gas revenues, which had declined by 30 percent.

Russia's budget plan aims for a 3 percent deficit in 2016 but Deputy Finance Minister Alexei Lavrov said on Tuesday the ministry is now aiming for a deficit of 3.0-3.3 percent.

Siluanov said the 2016 budget deficit was likely to be 420 billion rubles ($6.5 billion) more than envisaged in the budget, which had assumed an average Urals oil price of $50 per barrel.

"We see that the price of oil today is quite different, $37-38 per barrel since the beginning of the year, and according to the estimate for the year we expect around $40," Siluanov told the upper house of parliament.

He said the government had prepared proposals for spending cuts, as a result of which the finance ministry is cutting the funds it provides to other ministries. "The volume of the blocked resources is 460 billion rubles," he said.

($1 = 64.3234 rubles)

(Reporting By Darya Korsunskaya; Writing by Jason Bush; Editing by Katya Golubkova)