Obama says Russia is 'violating basic principles of international law' in the crisis in the Ukraine and said he was wary of a Ukraine, Russia ceasefire announcement today.
The Presidents comments in Estonia come after Ukrainian President Petro Poroshenko announced Russia and Ukraine had agreed to a ceasefire after a phone call.
However, Obama says time will tell whether the announced ceasefire would work.
"So far it hasn't helped because Russia pretends it's not controlling separatists. We haven't seen a lot of follow up on announced ceasefires," Obama told reporters in Estonia on Wednesday.
"Our preference is a strong, productive, cooperative Russia. The way to achieve that is by biding to international norms. "No realistic political settlement can be achieved if Russia says we're going to continue sending troops, arms under guise of separatists who are not home grown. "
He adds: "There's an opportunity here, let's see if there's follow up.
Obama added that EU and Western sanctions applied on Russia had a real affect on the country whilst Russia was "violating basic principles of international law." in sending troops in to the east of the country.
Russia has denied its supporting or has sent troops in to the Ukraine. Russian foreign minister Sergei Lavrov earlier called for an immediate ceasefire in the region.
Speaking about NATO maneuverers in the Baltics, Obama said the alliance would be unwavering it's in commitment to defending it's member states.
"Estonia will never stand alone. In response to Russia's actions in Ukraine, we'll contribute additional aircraft to Baltic Air Policing mission. We're continuously rotating aircraft in the Baltics."
Obama added that additional air force units would be patrolling the Baltic skies from the Amari air base in Estonia.
"Because we've stood together, Russia has paid a heavy price for it's actions," Obama adds.
Praising Estonia's contribution to world affairs, Obama added: "This nation of 1.3 million truly punches above it's weight."
Estonia's President Toomas Hendrik Ilves was more direct in his remarks over Ukraine. He said: "This is Russian aggression. The EU and U.S. are ready tot take further restrictive measures on Russia's behavior.
"We must also continue to support Ukraine by providing country with assistance it needs."
He adds: "We take our NATO commitment very seriously."