Russian President Vladimir Putin on Tuesday urged Kiev to extend the shaky truce with insurgents in eastern Ukraine and launch talks despite them shooting down a helicopter with nine on board.

The Russian strongman said he had asked senators to rescind a resolution allowing him to invade Ukraine in order to encourage a "peace process" but vouched at the same time to always protect the interests of Russians in the neighboring country.

U.S. President Barack Obama on Monday warned Vladimir Putin that Russia would face new sanctions if it failed to both stop the flow of weapons into Ukraine and halt support for separatists.

The White House said that Obama delivered the warning in a telephone call with the Russian leader, in which he called for "concrete actions" by Moscow to de-escalate the situation.

Lithuania's president compared Russian President Vladimir Putin to Hitler and Stalin in comments on the Ukraine standoff that were published by a German news magazine on Monday.

Asked by Focus weekly if it went too far to liken Putin to Stalin, or to Hitler as former U.S. secretary of state Hillary Clinton reportedly did, Dalia Grybauskaite emphatically said it wasn't.

Russian President Vladimir Putin on Sunday called on Ukraine's leadership and rebels to start genuine dialogue, saying Kiev should halt military operations and guarantee the rights of Russian speakers in the separatist east.

"It's necessary to start detailed, substantial dialogue," Putin told reporters on Sunday, adding Moscow would support a peace plan drawn up by the Ukrainian leader.

Ukraine's unilateral ceasefire hung in the balance Sunday after clashes engulfed the separatist east and Russian President Vladimir Putin put troops on "full combat alert".

The resurgence of violence in the 11-week pro-Russian uprising threatening to splinter the ex-Soviet state came as Washington accused the Kremlin of covertly arming the rebels and sternly warned Putin against sending troops into Ukraine.

Ukraine's unilateral ceasefire hung in the balance on Saturday as clashes engulfed the separatist east and Russian President Vladimir Putin questioned the new Western-backed leader's claimed commitment to peace.

The resurgence of violence in the 11-week pro-Russian uprising threatening to splinter the ex-Soviet state came as Washington accused the Kremlin of covertly arming the rebels and sternly warned Putin against sending troops into Ukraine.

Russian President Vladimir Putin will fly to Brazil next month for the final game of the football World Cup, the Kremlin confirmed Friday.

"The president is scheduled to attend the final match of the World Cup as Russia is the host of the next world championship in 2018," top foreign policy aide Yury Ushakov told reporters.

Russian President Vladimir Putin on Friday offered Iraqi Prime Minister Nuri al-Maliki Moscow's total backing for the fight against jihadist fighters who have swept across the Middle East country.

"Putin confirmed Russia's complete support for the efforts of the Iraqi government to speedily liberate the territory of the republic from terrorists," the Kremlin said in a statement following a phone call between the two leaders.

Russian President Vladimir Putin and his U.S. counterpart Barack Obama will discuss the situation in Ukraine, Iraq and Syria "in the coming days," a top aide said on Friday.

Speaking to reporters, Putin's top foreign policy adviser, Yury Ushakov, did not provide further details about the upcoming phone call.

Ukraine's new Western-backed president on Friday released a sweeping peace plan for curbing a pro-Russian uprising in the separatist east that is threatening the ex-Soviet country's survival.

The 14-point initiative's publication followed two calls made by President Petro Poroshenko to Vladimir Putin within 72 hours in the belief that no truce could work without the support of the Russian strongman.