President Obama's address on Wednesday at the Palais Des Beaux-Arts in Brussels followed talks with European Union and NATO leaders on Russia's military backed annexation of the Crimean Peninsula from Ukraine.
In making the case for a united stand against what he characterized as Russian aggression, Obama borrowed from the language that helped win him the White House for a second term.
"We believe in human dignity - that every person is created equal, no matter who you are, or what you look like, or who you love, or where you come from," he said.
Later, Obama reiterated criticism of Russian intolerance spawned by a law passed before the Sochi Olympics that outlawed promoting gay rights to children.
Western ideals and values of openness and tolerance would endure long past repression, he argued.
"Instead of targeting our gay and lesbian brothers and sisters, we can use our laws to protect their rights," he said. "Instead of defining ourselves in opposition to others, we can affirm the aspirations that we hold in common. That's what will make America strong. That's what will make Europe strong. That's what makes us who we are."
His comments came a day before Obama meets with Pope Francis in Vatican City in a visit that the White House says will focus on their shared commitment to helping the disadvantaged.
Earlier this month, the Pope reaffirmed the Catholic Church's opposition to gay marriage but suggested in a newspaper interview that it could support some types of civil unions.
While reiterating the church's longstanding teaching that "marriage is between a man and a woman," Francis said that "we have to look at different cases and evaluate them in their variety."
In the wide-ranging interview published March 5 in Corriere della Sera, an Italian daily, the Pope noted that state-sanctioned unions can result from the need to ensure rights such as access to health care.
The Catholic News Service called the comments "the first time a Pope has indicated even tentative acceptance of civil unions."
Francis, who marked his papacy's first anniversary on March 13, has sought to set a more tolerant tone for his 1-billion-member church.
Last June, the Pope refused to judge gay priests in comments that ricocheted around the world. He has also said that the church should not "interfere" in the spiritual lives of gays and lesbians.