Russia says it will focus its invasion of Ukraine on "liberating" the east, signalling a possible shift in its strategy.
The defence ministry said that the initial aims of the war were complete, and that Russia had reduced the combat capacity of Ukraine.
Russia's invasion appeared aimed at swiftly capturing major cities and toppling the government.
But it has stalled in the face of fierce Ukrainian resistance.
"The main tasks of the first stage of the operation have been carried out," said Sergei Rudskoy, head of the General Staff's main operations administration.
"The combat capabilities of the Ukrainian armed forces have been substantially reduced, which allows us to concentrate our main efforts on achieving the main goal: the liberation of Donbas," he added, referring to an area in eastern Ukraine largely in the hands of Russian-backed separatists.
Russia's military has been bombarding and trying to encircle key Ukrainian cities such as the capital Kyiv, which Gen Rudskoy characterised as an attempt to tie down Ukraine's forces elsewhere in the country while Russia focuses on the east.
Ukraine's President, Volodymyr Zelensky, said his troops had landed "powerful blows" on Russia and called on Moscow to recognise the need for serious peace talks.
"By restraining Russia's actions, our defenders are leading the Russian leadership to a simple and logical idea: talk is necessary. Meaningful. Urgent. Fair. For the sake of the result, not for the sake of the delay," he said.
The exact end goal of Russia's invasion has not been made explicit, but President Vladimir Putin described the aims as the "demilitarisation" and "denazification" of Ukraine, characterising the government's leaders as a neo-Nazi junta killing millions in a genocide of Russian speakers.
The claims have no basis and Ukraine and its Western allies dismiss them as a pretext to carry out an unprovoked war.
Russian troops first tried to encircle the capital Kyiv. But after bombarding and then seizing several towns to the north-west they were forced back by Ukraine's military, which is now trying to surround thousands of Russian soldiers.
In a US assessment on Friday, a defence official said that Russia had made no progress in its advance on Ukraine's second largest city Kharkiv, and that Ukraine could recapture Kherson.
Russia's army has had greater success in the south, seizing towns and cities such as Kherson, and making some gains in the east.
Moscow now claims 93% of the Donbas region of Luhansk is under the control of Russian-backed separatists, with 54% of the other part of Donbas, Donetsk, in their hands. More than a third of the entire area was under separatist control before the war began.
Andriy Yermak, chief of staff to Ukraine's President Zelensky, cautioned against the suggestion that Russia had abandoned plans to seize the rest of Ukraine. "It's a big danger before war is finished to make a public prognosis, especially when you are fighting against one of the biggest armies in the world," Mr Yermak told the Financial Times.
What next for Russia's war?
Russia's announcement that it will focus on the "liberation of the Donbas" is likely to mean a more concerted effort to push beyond the "line of contact" that separates Ukrainian government-held territory in the east of the country from the Russian backed separatist "people's republics" of Donetsk and Luhansk.
Western officials believe the announcement implies that Moscow knows that its pre-war strategy has failed.
"Russia is recognising that it can't pursue its operations on multiple axes simultaneously," one official said.
As many as 10 new battalion tactical groups are being generated and put into Russia's operations, especially in the Donbas.
Western officials have been concerned for some time that Russia will attempt to encircle and envelop Ukraine's best fighting units, which are stationed along the line of contact.
If more Russian firepower, particularly air power, is concentrated in the east, those concerns will rise.
"I hope that's where the Western supply of arms will make a significant contribution to Ukrainian forces," one official said.
War in Ukraine: More coverage
In another development, Russia's defence ministry also announced that 1,351 servicemen had been killed and 3,825 wounded in Ukraine.
The number is far lower than the number of Russian casualties cited either by Ukraine or the US.
Western officials say a seventh Russian general has been killed in action. Analysts have previously suggested Ukraine may be deliberately targeting senior Russian military officers.
Ukraine's death toll since the war began is now well into the thousands, with 10 million people displaced within Ukraine and beyond its borders.
So far the UN has only confirmed 1,081 civilian deaths in Ukraine but the true number is far higher with 300 deaths reported in the attack on a theatre in Mariupol alone.
More than 3.7 million people have fled abroad, including 2.2 million to Poland. Russia says more than 400,000 have fled there too.