Speaking at the National Prayer Breakfast, Mr Blair told Mr Obama,
"You don't need cheerleaders but partners, not spectators but supporters,
" reported the BBC. He also advised the President that,
"The truest friends are those still around when the going gets toughest."
He continued, "Should it ever be tested, I hope
your faith can sustain you and your family."
Mr Obama gave praise to Mr Blair, whom he described as
a "very good friend".
He said Mr Blair had been "somebody who
did it first and perhaps did it better than I will do".
After Mr Blair's speech, he said, "I want to thank
my good friend Tony Blair for coming today.
He has been an example to so many people
around the world of what dedicated leadership can accomplish."
Mr Blair, who became a Catholic after his time as Prime Minister,
warned Mr Obama that the "public eye is not always the most congenial".
During his address he spoke of the "complete consternation"
he faced when he said he wanted to end a Prime Ministerial address
to the country with the words
"God Bless the British people".
"The system was aghast ...
As I sat trying to defend my words
a senior civil servant said with utter disdain,
'Really prime minister, this is not America you know.'"
Mr Blair has previously spoken of how he was afraid to talk
of his faith openly while he was Prime Minister
in case he was labelled a "nutter".