The Archbishop of Canterbury and the head of the Roman Catholic Church in England and Wales have arrived in Bethlehem on a Christmas pilgrimage.
A mass was held in the Grotto, thought to be Jesus' birthplace
Rowan Williams and Cardinal Cormac Murphy-O'Connor said they wanted to highlight how Israel's security measures were strangling the town.
Cardinal Murphy-O'Connor said Israelis and Palestinians needed international support to solve their problems.
Two other church leaders joined them on the four-day visit to the Holy Land.
The two archbishops travelled with Bishop Nathan Hovhannisian, of the Armenian Church of Great Britain, and the Rev David Coffey, of the Free Churches.
During their visit, they toured the Church of the Nativity and recited prayers in the grotto where Jesus is believed to have been born.
The church leaders are concerned about the effect of the barrier separating the West Bank from Israel on Christians living in the region.
Dr Williams said he also worries about an exodus of Christians from Bethlehem, changing its historic Christian nature.
"The sheer variety of communities within the Palestinian areas has always been one of its strengths.
"Co-existence has been easy and often fruitful.
"If that were to end that would be a very sad signal for the Middle East and the rest of the world."
Cardinal Murphy-O'Connor has previously said the town was "blocked in" by the Israeli security wall and checkpoints.
Speaking on BBC News 24, he said: "You cannot expect with this intractable position for the Israelis and the Palestinians to do it all by themselves."
He said the international community needed to help resolve their differences.
BBC correspondent Wyre Davis, who is in Bethlehem, said in a good year 50,000 pilgrims would visit Bethlehem, but this year fewer than 5,000 are expected.
He said some say this is a consequence of the wall, but Israel argues it is because of general violence in the region.