MOSCOW (CNN) -- Top Russian officials ended crucial talks with an International Monetary Fund delegation on Sunday without announcing a concrete deal for a multi-billion-dollar bailout.

However, the Russian government said the two sides agreed in principal on a loan package that could be worth as much as $15 billion. Moscow has sought the aid to help end its financial and economic crisis.

Russian Prime Minister Sergei Kiriyenko met for five hours with John Odling-Smee, head of the IMF department responsible for the former Soviet Union.

"The sides agreed on all key issues," Russian news agencies quoted a government spokesman as saying. Russian officials described the talks as "productive and successful."

The IMF did not comment after the talks, and sources told CNN that details of the agreement would be announced Monday. One source close to the discussions said technical details, including translations, still had to be worked out.

Some observers said the optimistic government statement appeared to be aimed at calming the markets, which have been anxiously awaiting the outcome of the talks.

The Russian government, beset by poor tax revenues, low world oil prices, financial market turmoil and the need to pay huge amounts of short-term domestic debt, says it urgently needs $10 billion to $15 billion in loans.

Neither side has officially confirmed the size of the loan package. A source close to the negotiations said it would be closer to the $15 billion figure.

Russia is under severe financial pressure. This month alone, it must pay off $6.5 billion in debts. Without the IMF loan, analysts say Russia would be forced to devalue its currency.

Russia is committed to keeping its ruble currency stable at just over six to the dollar, a policy it views as vital to preventing the hyper-inflation that mushroomed after the collapse of the Soviet Union in 1991.

Russian President Boris Yeltsin has said that the crisis, which has sparked mass protests over unpaid wages, was dangerous socially and politically. Many protesters demand resignations of both Yeltsin and his government.

Intensive lobbying by Yeltsin with leaders of G-8 countries last week apparently paid off. Yeltsin telephoned his fellow leaders, including U.S. President Bill Clinton. Russian sources said influence from the countries, especially the United States, helped to move things forward.

But the IMF also has been holding Russia's feet to the fire, requiring it to prove it is serious about economic reform. The Russian government under Kiriyenko has been pushing Parliament to pass an anti-crisis stabilization plan that would cut the deficit and increase tax collection.

The lower House of Parliament will hold an extraordinary session on Wednesday to consider the measures. Yeltsin has warned that if Parliament does not pass the anti-crisis plan, he will implement it by decree.

Deputy Prime Minister Boris Nemtsov recently estimated Russia's total state debt at $200 billion and said every third ruble of the budget goes toward servicing debt.

The dilemma facing Russian fiscal policy is how to move forward with economic development while both paying back the debt and propping up the ruble.

Moscow Bureau Chief Jill Dougherty, The Associated Press and Reuters contributed to this report.