Russia's state-controlled natural gas company "Gazprom will only send gas in the amounts that the Ukrainian side has paid for a month in advance" under the changed sale terms being contemplated, Putin said at a government meeting according to televised excerpts.
"They will receive as much as they have paid for," he said.
Russia says Ukraine now owes it USD 2.2 billion for natural gas supplies, and Gazprom last week demanded that Ukraine "take immediate measures" to settle the debt.
Putin however said that for now Russia would refrain from doing so, citing Ukraine's economic difficulties and Moscow's ongoing talks with the European Union.
Earlier this month, Gazprom announced it was raising the price of gas exports to Ukraine by more than a third, scrapping a previous discount amid soaring political tensions between the two ex-Soviet countries.
Ukraine now has to pay USD 485 dollars for 1,000 cubic metres of gas, the highest price of any of Gazprom's clients in Europe.
Speaking at the government meeting, Putin added that Russia was not in a position to prop up Ukraine's struggling economy indefinitely.
"The situation today is strange to say the least. As we know, our partners in Europe recognise the legitimacy of Kiev's current authorities but are doing nothing to support Ukraine. Not a single dollar, not a single cent.
"The Russian Federation does not recognise the legitimacy of the authorities in Kiev but is still continuing to render it economic assistance and subsidise Ukraine's economy in the amount of hundreds of millions and billions of dollars," Putin said.
Putin also expressed hope that Kiev would not take any irreversible steps and Russia's diplomatic efforts would be successful.
"I hope that the acting (authorities) will not do anything that can't be fixed later," he said, expressing hope that Russian efforts to calm tensions through talks would have a "positive" result.