KIEV, June 24 - Ukraine's president warned Tuesday that he may terminate his weeklong cease-fire early after rebels downed a military helicopter, while Russia urged the Kiev leadership to extend the truce and launch talks with the rebels.

President Petro Poroshenko's statement came hours after pro-Russian insurgents in Slovyansk shot down the helicopter, killing nine servicemen, according to the Associated Press. The attack came despite Monday's pledge by the rebels to respect the cease-fire.

Poroshenko declared the cease-fire on Friday as part of a peace plan to end two-month fighting between the government troops and the rebels in eastern Ukraine.

The insurgents have fired on Ukrainian positions 35 times since the cease-fire was announced, Poroshenko's statement said, instructing Ukrainian soldiers to fire back "without hesitation" if attacked.

"The president doesn't exclude that the cease-fire could be lifted ahead of time, taking into account its constant violation by the rebels controlled from abroad," Poroshenko's office said.

Russian President Vladimir Putin, meanwhile, urged Ukraine's government to extend the cease-fire and launch talks with the rebels that would give people in the mostly Russian-speaking east a sense of security and protect their rights.

"We hope that the cease-fire will be extended and it will be used for substantive talks," Putin said on a trip to Vienna.

Speaking shortly after the helicopter was shot down, Putin blamed Ukrainian forces for breaking the cease-fire on Tuesday by launching an airborne raid in Slovyansk, the flashpoint in the two-month insurgency.

Putin did not mention the downing of the helicopter, which marked a sharp escalation of tensions amid a cease-fire that has mostly held since early Monday. The rebels pledged to respect it following talks later in the day.

Earlier Tuesday, Putin asked parliament to cancel a resolution, which he once favored, sanctioning the use of Russian military force in Ukraine — a move that reflected his desire to avoid a new round of Western sanctions.

Poroshenko heralded the Russian leader's move as a "practical step" toward bringing peace to a region roiled by a separatist insurgency.

A Kremlin statement said Putin had asked the head of Russia's upper house of parliament to cancel his March 1 request authorizing the use of force on Ukrainian territory. The pliant chamber is expected to quickly rubber-stamp the move Wednesday.

Putin said he made the decision to "help create conditions for peace process," but added that Russia will continue to protect the rights of Russian speakers in Ukraine. "I hope that armed forces will not be needed for that," he said.

Putin needs to show his support for Poroshenko's peace plan ahead of Friday's European Union summit to avoid further Western sanctions. The EU has warned it could introduce new sanctions that would target entire sectors of the Russian economy if Moscow fails to help de-escalate the crisis.

The Brussels-based ambassador of one EU member state, speaking on condition of anonymity because of the sensitivity of the subject, said Russia's actions appear finely calibrated to just fall shy of the threshold that would trigger retaliatory economic measures by the bloc that would really bite.

At the same time, Putin may feel that he no longer needs to maintain the threat of an invasion to protect Moscow's interests in Ukraine.

Poroshenko's peace plan contains promises of decentralization and guarantees for protection of rights of Russian speakers, which Russia has demanded from the start of the crisis. (ap/ez)