After talks with visiting French President Nicolas Sarkozy, Medvedev also said international discussions on the conflict in Georgia would be held beginning Oct. 15 in Geneva.
The talks, which lasted more than four hours, were a bid by Sarkozy to salvage the cease-fire deal he negotiated last month. The deal ended the short war in which Russian forces routed Georgia's military and occupied swaths of Georgian territory.
"I believe this accord is an accord that represents a maximum of what we could have done," Sarkozy said. "If all the conflicts around the world found themselves this way on the road to resolution the world would be more stable."
The Russian leader insisted that Russia is complying with terms of the cease-fire. He also alleged that Georgia's leader, Mikhail Saakashvili, had received "a blessing, either in the form of a direct order or silent approval" from the United States to launch an "idiotic action" against the other breakaway province of South Ossetia.
"People died and now all of Georgia must pay for that," Medvedev said.
He said Russian troops would pull out of the Black Sea port of Poti and nearby areas in the next seven days, but only if Georgia signed a pledge to not use force against the breakaway province of Abkhazia.
He also accused the United States of helping re-equip the Georgian military, which was decimated in the war.
Both South Ossetia and Abkhazia have had de-facto independence since they broke away from Georgian government control in the early 1990s.
One of the sticking points of talks, Sarkozy said, was the fact that Russia had recognized the two regions as independent, drawing international criticism.
"It is not up to Russia to recognize unilaterally the independence of Abkhazia and South Ossetia. There are international rules. These should be respected," he said.
Medvedev, however, said Russia would not revisit that decision.
"Our decision is irrevocable, the two new states have come to existence," Medvedev said. "This is a reality which all our partners, including our EU partners, will have to reckon with."
Sarkozy suggested that the talks, which lasted at least four hours, were difficult.
"Not everything could be resolved in four hours," he said.
However, Sarkozy said the four objectives he had sought in coming to Moscow had been reached, referring in particular to the decision to send E.U. observers.
"What was accomplished today, it was rather significant," he said.
"The retreat of Russian forces, and a precise timetable. That's done. The deployment of international observers. That's accepted," he said.
He suggested the other two had been successful too, the question of refugees and international discussions about the region, which are starting in Geneva.
Medvedev said that Russia wants to maintain constructive relations with the European Union and he said "the ball was now in our European colleagues' court."
"Everything is absolutely clear: We want both partnership and peace and hardly anybody wants a confrontation between Europe and Russia," he said.
"We don't want any kind of exacerbation of relations," he said.
That point was echoed by Sarkozky.
"The world will not again find itself in a cold war that we don't need. We will not launch into adventures of this nature without reflecting about it first," he said.
Sarkozy was slated to fly to the Georgian capital later Monday to meet with Saakashvili and present the update to the cease-fire plan.
The head of Georgia's Security Council, meanwhile, said Georgian authorities awaited a full report from Sarkozy but that "there are some heartening aspects" in what Sarkozy and Medvedev described.
Alexander Lomaia said it was "very important" that Sarkozy had persuaded Russia to commit to "a concrete timetable for the withdrawal of all forces from all of Georgian territory" outside South Ossetia and Abkhazia.
World Court Begins Georgia-Russia Case
Georgia accused Russia on Monday of a "campaign of harassment and persecution" in the separatist regions of South Ossetia and Abkhazia and urged the International Court of Justice to intervene to halt killings and forced expulsions.
The case opened a new legal front in the battle between Georgia and Russia for control of the regions and began as French President Nicolas Sarkozy led an E.U. delegation to Moscow for talks aimed at easing the standoff.
Georgia accuses Russian forces, local militias and mercenaries of conducting a campaign of murder, forced displacement and attacks on towns and villages that started in the early 1990s and culminated in last month's brief war.
Ethnic Georgians "are being forced out of their homes by a campaign of harassment and persecution," Tina Burjaliani, Georgia's first deputy minister of justice, told the court.
Georgia claims the campaign has left thousands of civilians dead and forced more than 300,000 from their homes.
Burjaliani said Tbilisi had filed its case "at a time of great distress in its history. A time when hundreds of thousands of its nationals are persecuted and displaced from their homes only because they are Georgians."
Burjaliani accused Russia of trying to undermine Georgia's independence "through a policy of divide and conquer ... that has ripped apart its delicate multiethnic culture."
Russia also accuses Georgia of crimes against humanity, for launching a massive attack last month on South Ossetia, killing Russian peacekeepers and dozens of civilians. Moscow says its military actions since are aimed at protecting its civilians. Before the war, Russia had given passports to many of the residents of South Ossetia, even though it is part of Georgia.
Outside the courtroom, Russia's ambassador to the Netherlands, Kirill Gevorgian, dismissed Georgia's case as "nonsense."