Officials with the Faith and Freedom Institute have dispatched a letter to the president, asking that he correct himself.

"While some may deem the words 'worship' and 'religion' to be synonymous, and thus interchangeable, they are most definitely not!" said the letter from Faith and Freedom Institute President Gary Dull, Vice President Dave Kistler and historian Don Kistler.

"The First Amendment of the United States Constitution uses the word 'religion' and states unequivocally that Congress cannot prohibit the 'free exercise' of said 'religion,'" the letter continues.

"Your use of the word 'worship' implies that we have freedom ONLY within the confines of structures set aside for religious expression (i.e., churches, synagogues, etc.). This is not only a gross departure from the original intent of the First Amendment, but is also the first step toward eliminating faith expression in the public marketplace."

The organization, which says its purpose is to provide educational support for the moral, spiritual, political and biblical foundations of the U.S., argued words have meaning.

"To some, that may not appear to be a great issue, but it steals away the language of the First Amendment of the U.S. Constitution and gives a different meaning to the freedom to practice our religion as we determine," the organization said.

Dull told WND the change in terminology is significant. "Worship" usually is done behind the walls and closed doors of a building set aside for that purpose. "Religion," on the other hand, includes the biblically mandated activity of declaring the Gospel to all nations.

Freedom of religion, he said, "actually means that we can practice religion in public space. Freedom of worship is more personal and often behind the doors of a church."

Dull said the institute staff first noticed the change in terminology at the November 2009 address by Obama in memory of the victims of a radicalized Islamic officer in the U.S. military who shot up a military base.

Since then, it's been a recurring statement, he said his staff has found. Besides Obama, the Democrat administration's use of it also has been spotted in Secretary of State Hillary Clinton's addresses.

It implies, Dull said, that Christians or those of other faiths should "keep inside your church buildings."

The letter asks Obama to "retract all past use of this incorrect and misleading phrase, 'freedom of worship,' and cease all future use of the same. We also call on you to acknowledge America's Christian heritage as is clearly evidenced in our Founding documents and the overwhelming abundance of statements from our Founding Fathers."

Dull warned what one generation tolerates, the next generation promotes.

The idea that Christianity is perfectly fine behind closed doors of a church building – but not really acceptable any longer in the public square – is a recurring theme in the myriad lawsuits that have sprung up in recent years over statements of faith by public officials, ceremonial prayers in public meetings, Christian student groups at schools and colleges and other places and times when the nation's Christian heritage traditionally has been recognized.

The issue also has arisen in the arguments over "hate crimes." Legislation was signed by Obama last year that created penalties for making members of groups – specifically homosexuals – feel bad.

A well-known atheist once told him, Dull reported to WND, that he had no objection to Christians or people of other faiths practicing their religion as long as they remained behind closed doors.