Obama in Estonia

Obama landed in the Estonian capital, Tallinn, early on Wednesday aboard Air Force One. He is due to meet Baltic leaders, in what is a symbolic show of solidarity with Eastern Europe while emphasizing Washington's commitment to the security of the Baltic states.

It comes a day ahead of a NATO summit in Newport, Wales, in which Obama and Western allies will approve plans to position at least 4,000 troops and military equipment in the region. That plan is an attempt to calm growing insecurity particularly among Baltic states, nervous about the Russian-backed military intervention in eastern Ukraine.

While Ukraine is not a part of NATO, alliance members in Eastern and Central Europe fear they could be Moscow's next targets, prompting the 28-nation bloc to come up with a more robust response.

Russian President Vladimir Putin has claimed the right to intervene on behalf of Russian speakers if Moscow believes their rights are under threat. Estonia, Latvia and Lithuania - all former Soviet republics that are now NATO members - have significant Russian minorities.

In 1997, NATO and Russia signed an agreement in which the Western alliance agreed to not permanently station a substantial number of combat troops in Eastern Europe. On Tuesday, Moscow warned NATO against establishing a permanent presence near Russia's borders, saying it would view such a move as a threat.

"The fact that the military infrastructure of NATO member states is getting closer to our borders, including via enlargement, will preserve its place as one of the external threats for the Russian Federation," Mikhail Popov, deputy director of Russia's national security council, told the RIA Novosti news agency.

Ukraine officials say their army is locked not only in a conflict with pro-Russian separatists, but also with the Russian military. Unverified reports on Tuesday said that Russian military forces had been spotted in two major rebel-held cities in eastern Ukraine.

Putin has denied that his forces are invading Ukraine, and accusations that Moscow has sent troops and weapons to support pro-Russian insurgents.

Putin and Poroshenko discuss crisis

The Kremlin said on Wednesday that Russian President Vladimir Putin and Ukraine's Petro Poroshenko discussed ways to end the Ukraine conflict.

"The heads of state exchanged opinions about what needs to be done first in order to bring an end to the bloodletting in the southeast of the country as soon as possible," said Putin's spokesman Dmitry Peskov.

"The views of the presidents of the two countries about possible ways out of this difficult crisis overlap to a considerable degree," Peskov said.

jr/jm (AFP, AP)