Former Labour prime minister said he was determined to be part of the debate as he passionately believes Brexit is mistake.
Speaking at the Global Education and Skills Forum in Dubai, Mr Blair added now was not the time for him to comment on whether Theresa May should resign.
He was asked by Varkey Foundation chairman, Vikas Pota, whether he agreed with Tory peer Lord Gadhia that Mrs May will not last to the end of the week as leader of the country.
Mr Blair replied: "I have done the job of being prime minister, and I know how difficult it is. Frankly, she doesn't need me making it anymore difficult in this particular moment in time."
He added: "The one thing I do say to everyone though is that my country is going through a really difficult period, that's for sure, but don't write us off.
"It has been a big mess, we are in a lot of trouble, it has evoked a national crisis."
"I absolutely promise you one way or another - I obviously have very strong views about Brexit - but whatever happens on Brexit, one way or another Britain will get back on its feet again, will be a serious country again.
Mr Blair said Britain is in "a moment of real crisis" and if a leader is struggling to get the support of those around, it becomes "very challenging, very difficult, if not impossible".
He was questioned on whether he was grateful to have a degree of separation from UK politics in the current climate.
Mr Blair said it is when things are really bad that you want to be involved.
He continued: "It's an odd thing about politics - I would say the journey of politics is you start at your least capable and most popular, and you end at your least popular and most capable."
"And partly what happens over time is you do learn a lot from the process of being in government."
Asked by the Press Association whether he thought Mrs May was now at her "least popular and most capable", the former prime minister replied: "I am not sure about that one."
Mr Blair further explained that while he was no longer on the front line, sometimes even after you leave, it important to use what you've learned in government and inform the debate.
He said: "This is why on the Brexit thing, even though I am not on the front line any more, I believe so passionately it is a mistake for my country, that I feel absolutely determined to be part of it."