Justin Welby was speaking at the 2017 launch of a global prayer movement named 'Thy Kingdom Come' which encourages Christians to pray between Ascension and Pentecost for the Holy Spirit to aid Christian evangelism.
He said the project was "not an Anglican thing, it's not a Church of England thing, it's certainly not an Archbishop thing. It's a God thing".
Speaking during the launch at Lambeth Palace today the Archbishop said, "I have the most privileged job on the face of the planet. And I do the most extraordinary things, but I cannot remember in my life anything I've been involved in...where I've sensed so clearly the work of the Spirit. It's nothing to do with the denomination or me, or geography, skill, intellect. It's everything to do with Jesus and that's why I'm so excited about it."
Justin Welby said he'd estimated 5,000 people might engage with Thy Kingdom Come when it first launched last year but was shocked when 100,000 people got involved.
"We were astonished at the way it took off last year and the way God seemed to say 'it's nothing to do with you, I'm going to make this happen.'"
Speaking about Thy Kingdom Come's global impact, the Archbishop said, "God seems to be blowing by his Spirit to say 'Pray for evangelism. In whatever way you choose, pray'."
"When the Spirit is blowing, hoist the sails. Don't mess with it, don't control it. Go with the wind..."
Churches and individuals across the world are being encouraged to join the movement by praying between 25th May - 4th June. Large scale events will be held at Cathedrals and individuals are already being encouraged to commit to praying by signing up online at thykingdomcome.global and downloading free resources.
Emphasising the cross-denominational nature of the initiative and admitting he was "namedropping a tiny bit", Justin Welby said he'd met the Pope in October and the Catholic Church would be joining in.
The Archbishop shared openly about his own ministry explaining, "I spend a great deal of my life in situations where I don't know what to do or what to say. Where I'm well beyond any point where I know what to do...Prayer happens when we have a challenge we can't meet by our own resources.
"None of us have the resource to bring someone to living faith in Jesus Christ. Our cupboards are bare so we have to go to the one who has everything we need and ask for it. Thy Kingdom Come is essentially that in practice. It's the task set before us - not by me but by Jesus - he says to the Apostles you are my witnesses."
"Nobody else is going to be witnesses. If we don't do the witnessing there is no 'plan B'. There's no back up. So we have to pray 'come Holy Spirit' because the Spirit is the one who inspires our words. It's the Spirit who opens ears and warms hearts.
"This is why prayer is so important: It's not about us, it's about Jesus. Good news can only be proclaimed in the power of the spirit. Good news can only be received through the work of the Spirit."