Christian leaders are promising their prayers for Joe Biden after he was sworn in as president on Wednesday. 

The inauguration day passed peacefully as Biden called for unity and promised to be a president "for all Americans". 

Russell Moore, president of the Ethics & Religious Liberty Commission of the Southern Baptist Convention and a longstanding Trump critic, congratulated Biden on Twitter. 

"You have my prayers for blessing, wisdom, health, and success in leading our country," he said. 

Johnnie Moore, president of the Congress of Christian Leaders, quoted from Jeremiah 29:7, which calls on believers to pray for the city so that they too will prosper. 

He also quoted 1 Timothy 2:1-2, telling Christians to pray for those in authority. 

"You can count on my prayers & the prayers of tens-of-millions of Evangelicals whose commitment to pray for our nation & its leaders knows no politics," Moore said. 

Prior to the inauguration, loyal Trump supporter and evangelist Franklin Graham had asked Christians to make Wednesday "a day of prayer — for peace and calm, and praying for our new leaders." 

Biden started inauguration day with Mass at the Catholic cathedral in Washington DC, St Matthew the Apostle. 

The homily was delivered by Kevin O'Brien, president of Santa Clara University, a Jesuit university based in Silicon Valley.

He said Biden's public service had been "animated by the same conviction" as Jesus "to help and protect people and to advance justice and reconciliation, especially for those who are too often looked over and left behind, the people whose voices you raised in the campaign and throughout your public life." 

He said this was Biden's "noble commission" and quoted Phil 4:4-9, which promises the peace of God to those who pray. 

"After too much darkness, the dawn breaks today, this inaugural day. Let us meet the dawn together, brothers and sisters, emboldened by our faith and civic conviction, full of promise and hope," he said.