President John Adams declared May 9, 1798, to be "a day of solemn humiliation, fasting, and prayer," during which citizens of all faiths were asked to pray "that our country may be protected from all the dangers which threaten it". 
President Abraham Lincoln issued a proclamation that "set apart a day for National prayer and humiliation"[because] we have grown in numbers, wealth and power, as no other nation has ever grown. But we have forgotten God - forgotten the gracious hand which preserved us in peace, and multiplied and enriched and strengthened us; and we have vainly imagined, in the deceitfulness of our hearts, that all these blessings were produced by some superior wisdom and virtue of our own. Intoxicated with unbroken success, we have become too self-sufficient to feel the necessity of redeeming and preserving grace, too proud to pray to the God that made us!
behooves us then, to humble ourselves before the
offended Power, to confess our national sins, and to pray for clemency
forgiveness"I do, by this my proclamation, designate"a day of national
humiliation, fasting and prayer" in
the hope that God would respond by restoring "our
divided and suffering Country, to its former happy condition of unity
President Obama's National Day of Prayer PROCLAMATION asked "for wisdom, compassion, and discernment of justice as we address the great challenges of our time. We are blessed to live in a Nation that counts freedom of conscience and free exercise of religion among its most fundamental principles"[and] let us remember in our thoughts and prayers those people everywhere who join us in the aspiration for a world that is just, peaceful, free, and respectful of the dignity of every human being."
"Prayer is also the struggle for human justice. It is the fight to remove killing stereotypes, to hurl back ignorance of prejudice, and to protect the holiness of creation. Prayer is the corporate, political act that serves to equalize opportunity so that privileged and underprivileged might have the same chance."
Thomas Merton, 20th century Trappist monk poet, social critic and mystic warned Christians that,"The duty of the Christian at this time is to do the one task God has imposed upon us in this world today. The task is to work for the total abolition of war. There can be no question that unless war is abolished; the world will remain constantly in a state of madness. The church [meaning all Christians] must lead the way on the road to the abolition of war. Peace is to be preached and nonviolence is to be explained and practiced."Praying for an End to Nuclear Weapons
The United Nations opened a month-long conference in New York this week to review ways to contain the spread of nuclear weapons. Prior to the conference, leaders from several religious traditions gathered at an interfaith chapel across from the UN to pray for the abolition of all nuclear weapons. Christians, Jews, Muslims, Buddhists, and others offered prayers, chants, songs, and special readings. Watch excerpts of the service, where some of the participants included Buddhist peace activists; Roman Catholic Archbishop Joseph Mitsuaki Takami of Nagasaki, Japan, a survivor of the 1945 atomic bombing, who brought a scorched piece of a statue of Mary from the cathedral that was destroyed in the attack; a Shinto chant leader; Rev. Michael Kinnamon, general secretary of the National Council of Churches; a Native American prayer-song leader; Buddhist and Muslim readers; and Bishop Katharine Jefferts Schori, presiding bishop of the Episcopal Church.
See it here on PBS:
1. Adams, "A Proclamation," March 23, 1798; printed in the Philadelphia Weekly Magazine, March 31, 1798.4. Bishop John Shelly Spong, "WHY CHRISTIANITY MUST CHANGE OR DIE" page 147.