Russia has reportedly accused the United States of failing to uphold commitments it says were made during last year's summit between President Vladimir Putin and U.S.

President Donald Trump in Alaska, signaling growing frustration in Moscow over stalled diplomacy on Ukraine.

According to Reuters, three senior Russian officials have publicly complained over the past several days that Washington has not followed through on unspecified understandings reached during the August meeting.

Russian Officials Question US Commitment Kremlin aide Yuri Ushakov said Sunday that Russia had remained committed to the agreements reached at the summit, while the U.S. had not fully met its obligations, Reuters reported.

Russian Foreign Minister Sergei Lavrov went further on Tuesday, suggesting the Alaska meeting may have been used by Washington to buy time for Ukraine to strengthen its military position.