Lithuania's military intelligence service on Thursday said it estimated that Russia had enough resources to wage two more years of war in Ukraine.

"Russia had been accumulating weapons and equipment over the long years of the Cold War," military intelligence chief Elegijus Paulavicius told reporters.

"We estimate that (its) resources would last for another two years of a war of the same intensity as today," he added.

He noted that the assessment depended on the perspective that no foreign country would provide military aid to Moscow.

Russia has a large amount of weaponry stored in its reserves, which would allow them to "cause enormous damage and increase the costs of restoration," he said.

He spoke alongside his counterpart from civilian intelligence at a presentation of their annual report.

Beyond estimates of Russian resources, the report also suggested that Russia's mobilization last year showed that support for the war in Ukraine "is not as big as the regime's propaganda tried to make it seem".

"Dissatisfaction with the regime's policies is currently taking a passive form: mostly avoiding mobilization, complaining about poor provision and disarray in the army," the document said.

It also raised the possibility that Russia's failures on the battlefield, further mobilization and sudden deterioration of the economic situation "would have negative consequences for the stability of the regime".

Lithuania, a member of both the European Union and NATO, has been a major backer of Ukraine since it was invaded by Russia in February last year.