President Barack Obama has affirmed his faith and spoken out on the peril of those enduring religious persecution in his speech at the annual National Prayer Breakfast in Washington DC.

He called for the release of two prisoners who are currently imprisoned for their beliefs, urging North Korea to release American Christian missionary Kenneth Bae and Iranian-American Pastor Saeed Abedini.

Bae was motivated to show compassion to the people of North Korea by contributing to their economy in the form of tourism, and guided at least 15 tour groups, mostly made up of Americans and Canadians, into North Korea.

He was arrested in November 2012, accused of hostile acts against the state, and sentenced to 15 years of hard labour.

President Obama also urged Iran to release Christian Pastor Saeed Abedini, an Iranian-American Christian pastor who is now in one of Iran's most dangerous prisons. Abedini is a former Muslim who converted to Christianity in 2000. In Iran, Muslim converts to Christianity suffer discrimination in the hands of Christian authorities, and are not allowed to worship together with other Iranian Christians.

Abedini and wife Naghmeh together became prominent in the Iranian house church movement, in which Christians meet in unofficial gatherings.

With the election of Mahmoud Ahmadinejad in 2005, the government began to crack down on this movement, and the Abedinis moved to the United States.

On a previous visit to Iran, Abedini had been detained by the Iranian authorities and released only after signing a statement saying he agreed to stop church house activities in the country.

However, on a visit in 2012 he was formally arrested on charges of undermining national security and sentenced to eight years in prison.

Obama said the US would continue to stand for the rights of all people around the world to practise their faith "in peace and freedom".

"As we build the future we seek, let us never forget those who are persecuted today, among them Americans of faith," he said.

"We pray for Kenneth Bae, a Christian missionary who's been held in North Korea for 15 months, sentenced to 15 years of hard labor. His family wants him home. And the United States will continue to do everything in our power to secure his release because Kenneth Bae deserves to be free.

"We pray for Pastor Saeed Abedini. He's been held in Iran for more than 18 months, sentenced to eight years in prison on charges relating to his Christian beliefs. And as we continue to work for his freedom, today, again, we call on the Iranian government to release Pastor Abedini so he can return to the loving arms of his wife and children in Idaho."

The President's statement comes just days after Reverend Patrick J Mahoney of the Christian Defense Coalition spoke with White House Press Secretary Jay Carney about Abedini's plight.

The American authorities have been criticised in the past for failing to press the release of the prisoners, and many were encouraged by Obama's words.

Reverend Rob Schenck, of the Evangelical Church Alliance said, "This is the breakthrough so many have hoped for, prayed for, and worked for, for so long. This call by the President needed to happen. We are enormously relieved to hear it and thank the President for taking a risk in saying it publicly."

First Lady Michelle Obama and Vice-President Joe Biden also attended the annual gathering along with foreign dignitaries, including President Michel Martelly from Haiti and President Bujar Nishani from Albania. Representative Janice Hahn and Representative Louie Gohmert co-chaired this year's breakfast.

Open Doors USA President and chief executive Dr David Curry was also encouraged by President Obama's speech.

"With the number of martyred Christians almost doubling last year from 1,201 to 2,123, according to Open Doors researchers, it is past due for a new focus in the State Department and our entire government to support the value of religious freedom worldwide and in our own country," he said.

Curry adds that Open Doors USA has been encouraging President Obama to quickly name a qualified person to fill the important position of Ambassador of International Religious Freedom at the State Department. Obama said during the event that he would make that appointment a priority.

In his speech, the President also affirmed his Christian faith and the difference it has made to his life.

He said: "So here we put aside labels of party and ideology, and recall what we are first: all children of a loving God; brothers and sisters called to make His work our own. But in this work, as Lincoln said, our concern should not be whether God is on our side, but whether we are on God's side.

"And here we give thanks for His guidance in our own individual faith journeys. In my life, He directed my path to Chicago and my work with churches who were intent on breaking the cycle of poverty in hard-hit communities there.

"And I'm grateful not only because I was broke and the church fed me, but because it led to everything else. It led me to embrace Jesus Christ as my Lord and Savior."