U.S. President Barack Obama has reaffirmed the United States' "unwavering" commitment to the security of Poland and other Eastern and Central European NATO allies after Russia's intervention in Ukraine.
In a speech in Warsaw on June 4, Obama said: "Poland will never stand alone. Estonia will never stand alone. Latvia will never stand alone. Lithuania will never stand alone. Romania will never stand alone."
Obama is in Warsaw for events to commemorate Poland's first democratic elections in 1989.
Addressing a crowd in Castle Square, Obama drew parallels between events in Poland 25 years ago and the current situation in Ukraine.
He said that "the days of empire and spheres of influence are over" and that bigger countries "must not be allowed to bully the small, or impose their will at the barrel of a gun."
He also said that "the stroke of a pen can never legitimize the theft of a neighbor's land," adding, "We will never accept Russia's occupation of Crimea or its violations of Ukraine's sovereignty."
He said Ukraine needs strong ties with Europe and Russia, but he said the people of Ukraine -- like those in all countries -- have the right to determine their own future.
He said "further Russian provocations will only mean more isolation and costs for Russia."
The crowd of some 6,000 people frequently interrupted Obama's speech with bursts of applause.
Earlier in the day, Obama met with Ukraine's President-elect Petro Poroshenko in Warsaw.
Obama said Poroshenko was a "wise choice" to lead Ukraine during what he called "this difficult period."
Speaking to reporters after the meeting, Obama said the two discussed how Washington can help train the Ukrainian military and law enforcement and ways for Ukraine to reduce its energy dependence on Russia.
Simultaneous to the meeting, the United States announced it would send Kyiv an additional $5 million in equipment that could help in its battle against armed pro-Russian separatists in the east. The aid will include body armor and night-vision goggles.