MOSCOW (Reuters) - Russia's domestic borrowing program will be completed as planned this year and the government is confident it will be able to quadruple its borrowings in 2017, Russian Finance Minister Anton Siluanov told journalists on Thursday.

Russia's budget deficit has widened as oil prices fell sharply from the 2014 highs of $115 per barrel to around $50 currently and the West imposed sanctions over the Ukraine crisis.

According to a finance ministry proposal, seen earlier by Reuters, the ministry plans to increase net domestic borrowing to 1.29 trillion rubles in 2017 from 300 billion rubles this year.

Siluanov confirmed the increase.

"Our (next year's) objectives envisage that the net borrowing will increase four times with limited spending from reserves funds", he said.

Siluanov also said he hoped there will be more foreign investors on the Russia's debt market buying domestic bonds.

Russia will exhaust one of its two sovereign funds next year while a third of another of state's funds will be spent over the next three years, according to a finance ministry proposal. The funds are aiming to cover a shortfall in the state budget and pension system.

Siluanov, speaking to journalists, said the cabinet cannot allow the depletion of Russia's reserves funds. He said the funds would run out if the government keeps on cleaning out state's rainy day coffers with a pace it has been doing it recent years.

"They (reserves funds) are not inexhaustible. Also, we cannot allow to substitute reserves fund spending for borrowing which are rising".

Siluanov also said that the government planned to slash the state budget deficit by 1 percentage point of gross domestic product annually in 2017-2019.

(Reporting by Darya Korsunskaya; Writing by Denis Pinchuk; Editing by Raissa Kasolowsky)