The survival of the world is at stake if Muslims and Christians cannot make peace with each other, Islamic scholars have told the Pope.

In a letter addressed to Pope Benedict XVI and other Christian leaders, 138 prominent Muslim scholars from every sect of Islam urged Christian leaders "to come together with us on the common essentials of our two religions", spelling out the similarities between passages of the Bible and the Qur'an.

"If Muslims and Christians are not at peace, the world cannot be at peace. With the terrible weaponry of the modern world; with Muslims and Christians intertwined everywhere as never before, no side can unilaterally win a conflict between more than half of the world's inhabitants. Our common future is at stake," the letter said. "The very survival of the world itself is perhaps at stake."

Scholars used quotations from the Bible and the Qur'an to illustrate similarities between the two faiths such as the requirement to worship one God and to love one's neighbour.

The letter, A Common Word Between Us and You, also referred to wars in Muslim-majority countries by urging western governments not to persecute Muslims.

"As Muslims, we say to Christians that we are not against them and that Islam is not against them - so long as they do not wage war against Muslims on account of their religion, oppress them and drive them out of their homes."

The letter was issued by Jordan's Royal Aal al-Bayt Institute for Islamic Thought following its annual convention last month in Amman. Many of the signatories are grand muftis who each have tens of millions of followers. There are four British supporters, including the Cambridge academic Abdal Hakim Murad Winter.

At the UK launch, Aref Ali Nayed, one of the British signatories, warned people not to get "too hung up" on expecting an answer from the Pope.

Dr Nayed, a senior adviser to Cambridge University's interfaith program, said: "Every person who extends his hand ... would like something in return but we're offering this as free love. It's not a competition. It's not about reciprocity."

It is the second open letter from the institute to the Vatican. The first was sent after the Pope's Regensburg address last year, which angered Muslims when he quoted a Byzantine emperor who spoke of the Prophet Muhammad's "command to spread by the sword the faith he preached".

All the signs yesterday were that the Roman Catholic leadership had been caught unawares by the initiative. According to some sources in Rome, the Pope had not yet read the letter.

But someone involved in making the letter public told the Guardian last night that it had been sent on Monday so that the Vatican would have time to react before it was made public. The source said that an acknowledgement had been received from the Vatican on Tuesday evening.

The authors' approach is one that can be expected to appeal to Pope Benedict, whose papacy has seen a shift in the Vatican's attitude to dialogue with the Islamic world. The Pope views contacts with Muslims as urgent and essential. But he has also signalled his impatience with the polite exchanges between theologians that have characterised the dialogue so far. Instead, what he has privately suggested is an "ethical dialogue" in which the aim would be to single out principles that both sides share, and then try to build on those.

There are two main items on the Pope's agenda: the use of religion in the Muslim world to justify violence; and what is known as reciprocity, a codeword for granting Christians in Muslim countries the same freedoms as Muslims enjoy in the west.

The situation in this respect has been getting more critical. Christian Arabs are leaving Palestine, Iraq and other Muslim countries in growing numbers. At the same time, anti-conversion laws are being enforced from Egypt to Pakistan.

The Archbishop of Canterbury, Rowan Williams, one of the recipients, welcomed yesterday's commitment to further dialogue between the two faiths.

"The theological basis of the letter and its call to respect each other, be fair, just and kind to another are indicative of the kind of relationship for which we yearn in all parts of the world, especially where Christians and Muslims live together," he said. "It is particularly important in underlining the need for respect towards minorities in contexts where either Islam or Christianity is the majority presence."

The common scriptural foundations for Jews, Christians and Muslims would be the basis for justice and peace in the world, he added.

"The call should now be taken up by Christians and Muslims at all levels and in all countries and I shall endeavour ... to do my part in working for the righteousness which this letter proclaims as our common goal."

A Common Word coincided with the end of Ramadan, the Muslim month of fasting, and came days after the Vatican's official Eid message, which urged Muslims to respect people of all faiths and not exclude them on the ground of religion, race or any other personal characteristic.

Last night Tony Blair, the former prime minister, welcomed the letter. He said: "This is the only way, in the modern world, to make sense of different history and culture, so that, instead of defining ourselves by reference to difference, we learn to recognise the values we share and define a shared future."

Extract: 'Without justice between us there can be no peace'

The full text of the letter from Muslim leaders ran to 29 pages. They also issued an abridged text, which appears here in full.

In the Name of God, the Compassionate, the Merciful

A Common Word between Us and You (Summary and Abridgement)

Muslims and Christians together make up well over half of the world's population.

Without peace and justice between these two religious communities, there can be no meaningful peace in the world. The future of the world depends on peace between Muslims and Christians.

The basis for this peace and understanding already exists. It is part of the very foundational principles of both faiths: love of the One God, and love of the neighbour.

These principles are found over and over again in the sacred texts of Islam and Christianity.

The Unity of God, the necessity of love for Him, and the necessity of love of the neighbour is thus the common ground between Islam and Christianity.

The following are only a few examples: Of God's Unity, God says in the Holy Qur'an: "Say: He is God, the One! / God, the Self-Sufficient Besought of all!" (Al-Ikhlas, 112:1-2).

Of the necessity of love for God, God says in the Holy Qur'an: "So invoke the Name of thy Lord and devote thyself to Him with a complete devotion." (Al-Muzzammil, 73:8).

Of the necessity of love for the neighbour, the Prophet Muhammad said: "None of you has faith until you love for your neighbour what you love for yourself."

In the New Testament, Jesus Christ said: "Hear, O Israel, the Lord our God, the Lord is One. / And you shall love the Lord your God with all your heart, with all your soul, with all your mind, and with all your strength. This is the first commandment./And the second, like it, is this: 'You shall love your neighbour as yourself.' There is no other commandment greater than these." (Mark 12:29-31)

In the Holy Qur'an, God Most High enjoins Muslims to issue the following call to Christians (and Jews - the People of the Scripture):

"Say: O People of the Scripture! Come to a common word between us and you: that we shall worship none but God, and that we shall ascribe no partner unto Him, and that none of us shall take others for lords beside God. And if they turn away, then say: Bear witness that we are they who have surrendered (unto Him)." (Aal 'Imran 3:64)

The words "we shall ascribe no partner unto Him" relate to the Unity of God, and the words "worship none but God", relate to being totally devoted to God.

Hence they all relate to the First and Greatest Commandment.

According to one of the oldest and most authoritative commentaries on the Holy Qur'an the words "that none of us shall take others for lords beside God" mean "that none of us should obey the other in disobedience to what God has commanded".

This relates to the Second Commandment because justice and freedom of religion are a crucial part of love of the neighbour.

Thus in obedience to the Holy Qur'an, we as Muslims invite Christians to come together with us on the basis of what is common to us, which is also what is most essential to our faith and practice: the Two Commandments of love.