Russia said Monday that President Vladimir Putin would not tolerate any ultimatums over Ukraine after a report said Germany had given him until Wednesday to agree a peace plan or face new sanctions.

"We've already said everything about the tone of the negotiations," Putin's spokesman Dmitry Peskov said on Russian radio.

At least 1,500 Russian troops and convoys of military hardware entered Ukraine over the weekend, the Ukrainian military said on Monday.

"One thousand five hundred Russian soldiers and 300 pieces of military equipment, including Grad missile systems, crossed the Ukraine-Russia border on February 7 and 8," Ukraine military spokesman Andriy Lysensko told journalists.

Russian President Vladimir Putin visits Egypt on Monday as Moscow looks to expand its reach in the Arab world's most populous country at a time when Cairo-Washington ties remain frayed.

His two-day trip will be Putin's first in a decade to Egypt and comes after a 2011 popular uprising that ousted ex-strongman Hosni Mubarak, who the Russian leader met in his previous visit in 2005.

German Chancellor Angela Merkel was Monday to brief U.S. President Barack Obama on the latest peace plan for Ukraine ahead of a four-way summit aimed at ending 10 months of bloodshed.

Foreign ministry officials from Ukraine, Russia, Germany and France were due to hold a preparatory meeting in Berlin after leaders agreed to push for the key meeting on a new peace deal Wednesday in Minsk, the capital of Belarus.

Turkey and Russia on Sunday tentatively agreed on the route for their planned Turkish Stream gas pipeline which Moscow hopes will replace its now scrapped South Stream project.

Turkish Energy Minister Taner Yildiz and Gazprom chief executive Alexei Miiller surveyed the route over the Black Sea during a four-hour ride by helicopter from Istanbul.

Russian President Vladimir Putin is behaving like a "mid-20th century tyrant", British Foreign Secretary Philip Hammond said Sunday, urging him to change track and save Russia's economy from further decline.

He told Sky News television that supplying arms from Britain to Ukraine would not be the right thing to do "at the moment", but insisted London's position would be kept under review.

As soon as Yevgeny left hospital after being wounded in the battle for Ukrainian rebel stronghold Donetsk airport, he made his way back to the terminal's apocalyptic surroundings and returned to fighting.

"I was wounded last month, during an assault to take the airport from Ukrainian forces," said pro-Russian separatist Yevgeny, 45, who has been fighting here for eight months.

U.S. Secretary of State John Kerry ruled out extending a March 31 deadline for Iran nuclear talks unless the basic framework of an agreement is hammered out, speaking in an interview aired Sunday.

"The only chance I can see of an extension at this point in time would be that you really have the outlines of the agreement," Kerry said in the interview on NBC's "Meet the Press" taped Saturday in Munich.

The United States is weighing "additional" assistance to Ukraine as it battles Russian-backed separatists, Secretary of State John Kerry said Saturday, while stopping short of saying Washington would send arms.

Kerry's comments came as Western leaders challenged Russian President Vladimir Putin to prove he wants peace in Ukraine, warning both sides a new Franco-German peace drive may be a "last chance" to stop all-out war.

Japanese Prime Minister Shinzo Abe on Saturday pledged to resolve a row with Russia over an island chain claimed by both nations and sign a bilateral peace treaty delayed since WWII.

Relations between Moscow and Tokyo have been strained for decades over of the status of four Pacific islands near Japan's north coast, known as the Southern Kurils in Russia and the Northern Territories in Japan.