"We want to really point out that Little Sisters of the Poor and people of faith live by a attractive calling and we will not let bureaucrats take away that calling or those rights", Trump said Friday.
"In America, we don't worship government, we worship God", Mr. Trump told the Value Voters Summit in Washington.
This will be the first time a sitting president has appeared at the conservative meeting.
The president also said he was "stopping cold" attacks on Judeo-Christian values. "If I'm president, you will see 'Merry Christmas" in department stores, believe me, believe me".
He added that people were saying "Merry Christmas" again and hoped Congress will pass his tax cut proposal as a festive gift to the American people.
Qatar, France neck-and-neck for UNESCO chief
Qatar's Hamad bin Abdulaziz al-Kawari and France's Audrey Azoulay are neck-and-neck in the race to head the UN's cultural body. However, UNESCO does not observe the kind of rotation by world region which is used when choosing a UN secretary general.
"America is a nation of believers and together we are strengthened and sustained by the power of prayer", Trump said.
However, SPLC president has sharply criticised the president for endorsing a hate group's event by participating as an official speaker at it.
President Donald Trump said Friday that the United States would maintain sanctions on Cuba and Venezuela until they restore political and religious freedom.
Last week, the Trump administration delivered on its commitment to religious liberty, with the Department of Health and Human Services rolling back on the ObamaCare contraceptive mandate, offering "full protection" to a range of companies and organizations that claim a "religious or moral objection" to providing birth control coverage.
Others scheduled to speak at the opening plenary are former Trump adviser Sebastian Gorka, current Trump counselor Kellyanne Conway, religious right activist brothers David and Jason Benham, former Congresswoman Michele Bachmann, and some current members of Congress: Mark Meadows, Mark Walker, Chris Smith, and Vicky Hartzler - the latter being an author of anti-transgender legislation.