President Barack Obama urged Russian President Vladimir Putin to put a halt to his aggressive actions in Ukraine in order to restore a working relationship with the United States and Europe. 

Obama made the statements during a visit to Warsaw, Poland, Tuesday, June 3, which is his first stop on his three-country European trip.

While the main purpose of Obama's trip to Warsaw is to celebrate the country's first democratic elections following the fall of communism 25 years ago, the trip holds a dual purpose. His visit to Warsaw is also intended to reassure American allies in Eastern Europe, who are uneasy about Russia's actions in Ukraine, most notably the annexation of Crimea.  

According to CNN, Obama called on Putin to withdraw all Russian troops from the Ukraine border, tell pro-Russia separatists to halt their militant actions and back the recently elected Ukrainian President-elect Petro Poroshenko. 

Obama said it may be possible to "rebuild some of the trust that has been shattered" if Russia acts responsibly. But, he said it will take "quite some time."

Moscow denies claims by the West and the government in Kiev that the pro-Russisa separatists are being coordinated and supplied by Russia. However, the U.S. still believes that Russia has a hand in the rebel violence in East Ukraine. 

Obama said the United States wants to broker good relations with Russia and does not want to threaten cutting all ties with the country. However, he noted that tough sanctions have been imposed on Russia because of the annexation of Crimea, and they could be maintained if Russia does not back the Ukraine government and fails to withdraw troops from the border. 

Russia has begun to pull some of its troops from the Ukraine border, which has the potential to ease tensions with the United States. However, Deputy National Security Adviser Ben Rhodes said that a friendly relationship with Russia is not imminent. 

"We have not yet seen Russia take the steps that are necessary to reduce those tensions," Rhodes said. 

Russia is seen as instigating and helping the pro-Russia separatists in eastern regions like Donetsk, which gained autonomy from Ukraine in a secession vote last month. 

Obama further noted that he will most likely see Putin in France at the end of the week to commemorate the 70th anniversary of D-Day. Obama and Putin are scheduled to have separate meetings with French President Francois Hollande Thursday in Paris. 

Obama is also meeting with Poroshenko Wednesday and will attend the G-7 summit in Belgium. 

While in Warsaw, Obama also announced that Congress is appropriating $1 billion for a "European Reassurance Initiative."

The initiative will allow the U.S. to begin more training exercises in Europe and pre-position military equipment. It will also allow the U.S. to strengthen ties with Moldova, Georgia and Ukraine so the countries can become allies and partners with the United States and NATO. 

Obama praised Poland for its commitment to NATO and encouraged other European allies to increase their defense capabilities in preparation for potential crises. He called Poland "one of your [NATO's] great friends and one of our strongest allies in the world."

The president will speak later with Polish Prime Minister Donald Tusk as well as with some other central and eastern European leaders. 

The president also fielded other questions about U.S. defense and foreign policy, including the recent exchange of five Taliban prisoners who were held at Guantanamo Bay for the return of former prisoner of war Army Sgt. Bowe Bergdahl. 

While Republicans criticized Obama for releasing the Taliban prisoners, Obama defended his decision, saying, "We don't leave men and women in uniform behind."

He expressed confidence that the exchange will not endanger U.S. national security interests, as Qatar, who helped broker the deal, will keep a close watch on the former Guantanamo prisoners. 

While the Europe trip is intended to reiterate America's global strength and commitment to its allies, Obama's critics argued that his approach to foreign policy is not bolstering America's image. 

Former Polish President Lech Walesa, whose Democratic movement helped bring a representative democracy to Poland after the fall of communism, contended that the global influence of the United States has weakened under Obama. 

"The superpower has not been up to the job," Walesa said in an interview with the TVN24 television network. "Therefore, the world is at a dangerous point, and maybe it really is the case that lots of bad things are happening in the world because there is no leadership."

Obama has defended his foreign policy strategies, standing by his decision to not have U.S. military intervention in Syria or Ukraine. 

"Because of American leadership, the world immediately condemned Russian actions; Europe and the G7 joined us to impose sanctions," Obama said in a speech at the U.S. Military Academy at West Point last week.