Russia will not force Ukraine to pay up front for gas until June 9, as the two sides continue talks over disputed gas prices.
Russia's state-controlled energy giant Gazprom announced the delay after Kiev paid off a chunk of its outstanding gas debt.
Following talks between the EU, Ukraine and Russia, Kiev transferred $786m (£470m, €578m) to Gazprom which cleared the way for further negotiations this week, beginning on Monday in Brussels.
Moscow had threatened to only deliver gas which Ukraine had paid for in advance from the beginning of June, a threat that has been delayed but could still result in Europe's gas supplies being disrupted.
Gazprom CEO Alexei Miller said switching to prepayment would depend on whether Ukraine pays off its $2.2bn gas debt for deliveries up to April, and makes progress on paying off its April and May debts.
"We welcome Ukraine starting to pay back its debt and postpone the pre-payment regime until 9 June," Miller said in a statement.
Russia and Ukraine became embroiled in the gas price dispute after pro-Russian former president Viktor Yanukovych was replaced by a pro-European interim government in Kiev. Russia almost doubled the price it charged Ukraine for gas, from $286 per 1,000 cubic metres to $485. Kiev has refused to pay the new price, saying it was "political".