Speaking in Vienna, Mr. Putin said that a weeklong cease-fire announced by President Petro O. Poroshenko of Ukraine on Friday and accepted by the separatists was insufficient. He said he had told Ukraine, “To declare a cease-fire is not enough; it is necessary to start substantive talks on the nature of the problem.”

Image Speaking in Vienna, President Vladimir V. Putin said that a weeklong truce announced Friday by President Petro O. Poroshenko of Ukraine was insufficient. Credit... Bernadett Szabo/Reuters

Mr. Putin said declaring a cease-fire and asking the rebels to disarm without addressing their long-term political grievances would yield nothing. The separatists want increased autonomy for Donetsk and Luhansk, and the government has said it is amenable to changes in the Constitution, though whether that will be enough to satisfy their opponents is an open question.

“If we see there are substantive talks, so that people in eastern Ukraine can finally understand how their legal interests will be guaranteed, then there is a high possibility of success,” Mr. Putin said at a news conference.

Mr. Putin said he was pleased by the first contacts on Monday between the Kiev authorities and the rebel representatives of Donetsk and Luhansk. “No big agreements were reached, but the fact that the dialogue has begun is a highly important moment,” he said.

The Russian president listed some of his standard complaints about Ukraine, including that it had not done enough to disarm a rabidly anti-Russian group called Right Sector. Without that, Mr. Putin said, it did not make sense to call on the militias in the east to disarm.

Mr. Putin was in Vienna to help push for a new, southern route for Russian gas exports in the face of European opposition. Russia is seeking alternative routes for its troubled pipeline to Europe through Ukraine, with the Ukrainian portion of the exports again shut down over pricing and political disputes.