May 24 (Reuters) - Russia's most senior lawmaker on Tuesday told the lower house of parliament to study the possibility of stopping the servicing of Russia's foreign debt, the day before a U.S.-issued licence that allows Moscow to make payments expires.

Russia's ability to service its debt is in focus as it faces the prospect of sovereign default after Western capitals imposed sweeping sanctions in the wake of what Moscow calls a "special operation" in Ukraine, launched on Feb. 24.

On Tuesday, a lawmaker from Russia's communist party said voters were unhappy with the fact that Russia was continuing to pay its debt obligations when its national reserves held abroad were frozen, and that this should be questioned.

Vyacheslav Volodin, the speaker of the lower house of parliament, ordered the financial market committee and the committee on budget and taxes to look into the matter.

"We'll discuss it after the budget and financial market committees examine it. We need to engage two committees, two heads are better than one," Volodin said.

Russia has so far been able to keep servicing its sovereign debt because of the special licence from the U.S. Treasury, which allows foreign bond holders to receive the payments despite the financial sanctions.

That exemption is due to run out on May 25, however, and U.S. Treasury Secretary Janet Yellen has signalled that it will not be extended.

Russian Finance Minister Anton Siluanov said last week that Moscow would service its external debt obligations in roubles if the United States blocked other options and would not consider itself in default as it had the means to pay.

Russian state-run lender Sberbank on Tuesday said it had made a coupon payment on dollar-denominated subordinated Eurobonds in roubles at the central bank exchange rate as sanctions prevented it from paying in foreign currency. (Reporting by Reuters; Editing by Kevin Liffey and Edmund Blair)