• Pope Benedict XVI to resign on February 28, Vatican says
• The pope is stepping down "because of advanced age,' he said in a statement
• He was elected pope in 2005. Read our full story here.

[Updated at 12:24 p.m. ET] President Obama issues the following statement on Pope Benedict's decision to step down: "On behalf of Americans everywhere, Michelle and I wish to extend our appreciation and prayers to His Holiness Pope Benedict XVI. Michelle and I warmly remember our meeting with the Holy Father in 2009, and I have appreciated our work together over these last four years.

"The Church plays a critical role in the United States and the world, and I wish the best to those who will soon gather to choose His Holiness Pope Benedict XVI’s successor."

[Updated at 8:57 a.m. ET] Cardinal Timothy Dolan of New York, president of the U.S. Conference of Catholic Bishops, issued the following statement about Pope Benedict's resignation:

"The Holy Father brought the tender heart of a pastor, the incisive mind of a scholar and the confidence of a soul united with His God in all he did. His resignation is but another sign of his great care for the Church. We are sad that he will be resigning but grateful for his eight years of selfless leadership as successor of St. Peter.

Though 78 when he elected pope in 2005, he set out to meet his people – and they were of all faiths – all over the world. He visited the religiously threatened – Jews, Muslims and Christians in the war-torn Middle East, the desperately poor in Africa, and the world’s youth gathered to meet him in Australia, Germany, Spain and Brazil.

He delighted our beloved United States of America when he visited Washington and New York in 2008. As a favored statesman he greeted notables at the White House. As a spiritual leader he led the Catholic community in prayer at Nationals Park, Yankee Stadium and St. Patrick’s Cathedral. As a pastor feeling pain in a stirring, private meeting at the Vatican nunciature in Washington, he brought a listening heart to victims of sexual abuse by clerics.

Pope Benedict often cited the significance of eternal truths and he warned of a dictatorship of relativism. Some values, such as human life, stand out above all others, he taught again and again. It is a message for eternity.

He unified Catholics and reached out to schismatic groups in hopes of drawing them back to the church. More unites us than divides us, he said by word and deed. That message is for eternity.

He spoke for the world’s poor when he visited them and wrote of equality among nations in his peace messages and encyclicals. He pleaded for a more equitable share of world resources and for a respect for God’s creation in nature.

Those who met him, heard him speak and read his clear, profound writings found themselves moved and changed. In all he said and did he urged people everywhere to know and have a personal encounter with Jesus Christ.

The occasion of his resignation stands as an important moment in our lives as citizens of the world. Our experience impels us to thank God for the gift of Pope Benedict. Our hope impels us to pray that the College of Cardinals under the inspiration of the Holy Spirit choose a worthy successor to meet the challenges present in today’s world."

[Updated at 8:12 a.m. ET] The Prime Minister of Ireland, Enda Kenny, has also weighed in:

"On behalf of the Government and people of Ireland, I would like to extend best wishes to His Holiness Pope Benedict XVI following his declaration today that he intends to step down from his office.

This is clearly a decision which the Holy Father has taken following careful consideration and deep prayer and reflection.

It reflects his profound sense of duty to the Church, and also his deep appreciation of the unique pressures of spiritual leadership in the modern world.

This is a historic day in the life of the Catholic Church and for the many millions of Catholics, both here in Ireland and around the world.

Pope Benedict has given strong leadership and great service to the Church and her people for many decades.

I know that all of their thoughts and prayers will be with the Holy Father at this time, and also with those who will shortly gather in Conclave to choose his successor.

[Updated at 8:11  a.m. ET] UK Prime Minister David Cameron has released a statement reacting to the pope's resignation."

"I send my best wishes to Pope Benedict following his announcement today. He has worked tirelessly to strengthen Britain's relations with the Holy See. His visit to Britain in 2010 is remembered with great respect and affection. He will be missed as a spiritual leader to millions."

[Updated at 7:29 a.m. ET] We've just received a statement from Archbishop Vincent Nichols, who is President of the Catholic Bishops' Conference of England and Wales, regarding the pope's decision.

"Pope Benedict’s announcement today has shocked and surprised everyone. Yet, on reflection, I am sure that many will recognise it to be a decision of great courage and characteristic clarity of mind and action.

The Holy Father recognises the challenges facing the Church and that 'strength of mind and body are necessary' for his tasks of governing the Church and proclaiming the Gospel.

I salute his courage and his decision.

I ask people of faith to keep Pope Benedict in their prayers. We Catholics will do so, with great affection and the highest esteem for his ministry as our Holy Father remembering with joy his Visit to the United Kingdom in 2010. Pray, too, for the Church and all the steps that must take place in the next weeks. We entrust ourselves to the loving Providence of God and the guidance of the Holy Spirit."

[Updated at 7:17 a.m. ET] "The pope was very concentrated. Evidently it was a solemn moment ... It was a very emotive speech," papal spokesman Father Frederico Lombardi says when a reporter asks about the pope's demeanor when making his resignation speech.

iReport: What's your reaction?

[Updated at 7:04 a.m. ET] Father Federico Lombardi acknowledges the unexpectedness of Pope Benedict's decision. "You have probably been surprised by this announcement today," he says. He also is promising further details and more briefings later.

Profile: Who is Pope Benedict XVI?

Does the pope 'resign' or 'abdicate'?

[Updated at 6:59 a.m. ET] The Vatican has released the full text of Pope Benedict's declaration.

Read more: Pope Benedict XVI Fast Facts

[Updated at 6:51 a.m. ET] Papal spokesman Father Federico Lombardi is giving a news conference explaining Pope Benedict's decision. Lombardi says Pope Benedict says he "is aware of the gravity of this act."

[Updated at 6:46 a.m. ET] Pope Benedict's announcement mean's he's the first pontiff to resign since Pope Gregory XII in 1415.

[Updated at 6:25 a.m. ET] Here's an excerpt from From Pope Benedict's statement to cardinals today announcing his resignation: "Strength of mind and body are necessary, strength which in the last few months, has deteriorated in me to the extent that I have had to recognize my incapacity to adequately fulfill the ministry entrusted to me."

[Updated at 6:19 a.m. ET] Pope Benedict is resigning "because of advanced age," he told the Cardinals of the Catholic Church Monday. Benedict is 85 and will turn 86 on April 16. He was elected pope in 2005.

[Posted at 6:14 a.m. ET] Pope Benedict XVI will resign on February 28, his spokesman Father Federico Lombardi told CNN today.

Lombardi did not give a reason for the resignation.

Benedict, the 265th pope, is the sixth German to serve as pope and the first since the 11th century. He has led church after the third-longest papacy in church history and during a time in which the church is declining in his native Europe but expanding in Africa and Latin America.