Edinburgh 2010 is taking place this week to commemorate the 100th anniversary of the World Missionary Conference held in the Scottish capital in 1910.
Addressing some 300 leaders from across the Christian denominations and traditions, the international director of the World Evangelical Alliance, Dr Geoff Tunnicliffe, said it would be "foolish" to think that all the issues that have traditionally divided the different streams of the church would be resolved during the four-day conference.
He appealed to delegates, however, to listen to one another with "love and respect" and to "build bridges rather than create chasms" during the conference.
"This conference's theme is 'Witnessing to Christ today'. We are not talking about some vaguely theistic or humanist agenda, but bearing glad witness to Jesus Christ, the second person of the Trinity," he said.
"There is no authentic Christian mission that does not bear witness to him in word and deed and character, both individually and corporately.
"And there is no authentic church that does not have a passionate commitment to mission, reflecting the heart of Father, Son and Holy Spirit."
Dr Tunnicliffe reminded Christian leaders that there was no corner of the world today where the mission of the church was complete and that there were many communities and people groups that had still not had anyone to bear witness to Christ among them. Europe in particular, he noted, is in desperate need of re-evangelisation.
He said: "God's calling to the whole church is to take the whole gospel to the whole world, and that call comes anew to us in every generation. I hope that in these few days we will ponder that, with humility and repentance, and with renewed commitment to bear witness to Christ, with the love of the Father and in the power of the Holy Spirit, in every corner of the globe."
While participants at the 1910 gathering came largely from the Protestant mission movement in North America and northern Europe, Edinburgh 2010 is being joined by representatives of all mainline churches and traditions, including Roman Catholic, Orthodox and Pentecostal, and Christian leaders from Africa, Asia and Latin America.
The General Secretary of the World Council of Churches, Dr Olav Fykse Tveit, said the prayer of those who gathered in 1910 – the prayer of Jesus in John 17 "that the church may be one" – was the same prayer for leaders gathered in Edinburgh today.
He said: "Mission and unity belong together. To be one in Christ is to witness together to Christ. We have a foundation going deeper than ourselves, our institutions or our traditions. We have a call which goes wider than our plans."
Dr Tveit reminded Christians that they were called to carry the cross together and bear one another's failures and shortcoming.
He said: "One hundred years after the Edinburgh conference in 1910 we are challenged to launch together a new beginning for common mission in the 21st century. We need to discern together what the call to carry the cross of Christ means for us today, as we witness together and find different ways to make it visible that we are called to be one."
Edinburgh 2010 will address a number of aspects of mission in the 21st century, including Christian mission among other faiths, mission and post-modernities and authentic discipleship.
The conference will culminate at the weekend with a Common Call to Christians and a celebration at the Assembly Halls of the Church of Scotland, the venue of the 1910 gathering. Keynote speaker will be the Archbishop of York, Dr John Sentamu.