The economic battle between Russia and Ukraine could enter the courtroom soon with Russian authorities calling Ukrainian officials “crooks.” Russian President Vladimir Putin said Wednesday if Ukraine does not repay $3 billion worth of debt by the Dec. 20 deadline a lawsuit would be filed, Reuters reported.

“If they [the U.S.] are so confident in the country’s solvency for the next year, then they could somehow participate during the last four years to share the risks,” Putin said Kremlin-backed news agency RT reported. “Fine. File the lawsuit.”

The Russian government purchased the $3 billion bond in early 2014 before then President Viktor Yanukovych was ousted from power during Ukraine's revolution. Putin has called on the U.S. to give guarantees on Ukraine’s debt repayments and offered an installment repayment plan.

Ukraine’s Finance Minister Natalie Jaresko was able to negotiate a 20 percent writedown on $18 billion worth of bonds as the country’s economy struggles, but the Kremlin has refused to take part, saying the bond was a loan to the government and should not be counted as part of debt restructuring. The International Monetary Fund, which is leading a $40 billion bailout in Ukraine, changed its lending rules Tuesday so that it can support countries that have not paid back creditors.

“It allows us to understand that if we are included in this policy and we unfortunately are not able to restructure the so-called Russian Eurobond, then the doors to IMF loan financing will not be closed to us,” Jaresko said, Reuters reported.

Russia was quick to react to the IMF’s decision, describing it as politically motivated. “I have the sense that they [Ukraine] won't pay it back because they are crooks,” said Prime Minister Dmitry Medvedev. “And our Western partners not only don't help but also interfere.”

The debt battle is the latest economic fight between the neighboring nations following sanctions and bans on areas ranging from air travel to food. Russia has continued to deny playing any direct military role in the war that broke out in Eastern Ukraine in April 2014 pitting Ukrainian government forces against Russian-backed separatists. The death toll in the conflict has reached over 9,000 with more than 20,000 people injured the United Nations reported Wednesday. Over 1.4 million people have been displaced by the war that has devastated Ukraine’s economic heartland.