His comments came with added punch as he delivered them in the heart of the Chinese capital during Beijing's Olympic moment.
China allows worship only in officially approved churches such as the one Bush visited Sunday with his wife, so millions of people pray privately in house churches to avoid detection.
The Chinese government has bristled at Bush's efforts as pointless meddling.
Bush spoke of the great joy he felt while worshipping in the church, where a children's choir performed "Amazing Grace" in English and Chinese. With the children surrounding him, he made a brief statement afterward on the steps outside the church to media standing in a pouring rain.
"It just goes to show that God is universal," Bush said. "No state, man or woman should fear the influence of loving religion."
Bush earlier entered the Protestant church to sustained applause. He sat near the front, next to first lady Laura Bush and their daughter, Barbara.
The service was delivered nearly entirely in Chinese, but Bush followed along and bowed his head in prayer with the other parishioners.
Juggling sports and strife on his whirlwind Olympic adventure, Bush was to meet later with Chinese President Hu Jintao amid persistent criticism over how China treats its own people. The U.S. president promised again to prod Hu to let people speak and pray freely without harassment. China says that is a matter it can handle without outside meddling.
Bush, who came to Beijing mainly to have fun at the Olympics, also now finds himself immersed in a conflict with China's neighbor to the north, Russia.
A grim and blunt president upbraided Moscow over its escalating standoff with a former Soviet state, Georgia. Bush questioned attacks in parts of Georgia away from South Ossetia, the breakaway province at the center of the fight.
"The violence is endangering regional peace," Bush said. He pushed Russia to embrace an international mediation effort by the United States and its European allies.
His schedule a day earlier juxtaposed moments light and somber, sometimes jarringly so.
He took a rigorous ride on the Olympic mountain biking course, had a try at beach volleyball and laughed it up with members of the U.S. women's softball team. The president enjoyed the sweat-soaked experience of hanging out with athletes in an unscripted way.
Later came the news that a Chinese man had stabbed the in-laws of the U.S. Olympic men's volleyball coach, killing one and injuring the other, and stabbed a tour guide, too. The assailant committed suicide by jumping from the tourist site the Americans were visiting.
Bush spoke on that topic and the rapidly changing events in Georgia. He warned of the seriousness of the military conflict and expressed sadness about the stabbing.
As scheduled, Bush then went back to rooting for his country's team. He took off the coat and tie and headed to the basketball arena to watch the U.S. women's team with his family.
More shifting between sports and diplomacy awaited Bush on Sunday, when he planned to attend men's and women's swimming competitions. By afternoon, the schedule had him at the Zhongnanhai Compound, the central government complex, for meetings with Hu, Chinese Vice President Xi Jinping and Premier Wen Jiabao.
Among the expected topics of discussion were counterterrorism, trade, economic markets, individual freedoms, and efforts to halt the nuclear weapons capability of Iran and North Korea.
No major announcements were anticipated.
Bush and Hu met just one month ago, at the summit in Japan of the world's economic powers. Standing together, Bush told reporters at the time that he and Hu "have constantly had discussions about human rights and political freedom. He knows my position."
Just in case, Bush has kept on it through his weeklong Asia trip.
In Thailand, Bush said the U.S. firmly opposes China's crackdown on political dissidents and human rights activists. The speech angered China's government, which responded by telling Bush not to intrude in its affairs.
Bush was careful to say that change will occur in China on its terms.
The State Department says local authorities in China handle the unsanctioned Protestant "house churches" differently throughout the country. Some are not bothered. Others are targeted for abuse, with leaders harassed, detained and beat, the department says.
"Only China can decide what course it will follow, but I'm optimistic about the prospects," Bush said in his radio address Saturday, taped in Beijing. "Young people who grow up with freedom in one area of their lives will ultimately demand freedom in other areas."
When Bush's diplomatic meetings conclude Sunday, it's back to the basketball arena.
This time it is the men's game between the United States and China. Several of the players from the U.S. men's team, including stars Kobe Bryant and LeBron James, showed up at the U.S. women's game on Saturday and caused a stir. Bush saw it and smiled.