Christians driven out of northern Iraq by Islamic State might be able to return to their homes this year, according to the Vatican's diplomatic representative in Iraq.

Archbishop Giorgio Lingua told a representative of Roman Catholic charity Aid to the Church in Need that he was cautiously optimistic but that the process would be very challenging.

"If they do return it won't be easy," he said. "Besides the reconstruction of destroyed houses and infrastructure, such as schools, it will be necessary first and foremost to restore the trust in Muslim neighbours which has also been shattered.

"Many Christians feel their neighbours betrayed them, because they looted their [abandoned] houses. So it will not only be necessary to repair homes, but also relationships."

He said the Iraq central government was working more effectively and was seeking to ensure that more parties were represented.

"Something has been put in motion; the new government is working well," he said. "A fundamental factor is the greater involvement of all groups. The country will never be free of terrorism as long as some ethnic and religious components are barred from the governing process. If a group is excluded it must not be assumed that they will not rebel."

The failure of former Shiite Prime Minister Nouri al-Maliki to create a government that included both Sunnis and Shiites is widely regarded as the main reason for the alienation of Sunnis and the growth of Islamic State. His position became increasingly untenable and he lost power last August to Haider al-Abadi.

Archbishop Lingua said that the position of Christians in Iraq depended on how the Government handed the crisis in Mosul and the Nineveh Plain.

"If the government manages to regain control there and implements a campaign of national reconciliation, then there will be a place for Christians in Iraq. If clashes persist, however, the weakest will pay the price, and these are always the minorities. We therefore have to hope that peace will return. This is where the international community comes in."

He stressed the need for humanitarian relief, saying that the cold winter was aggravating other difficulties. "At the present time the people mainly need heaters. There are reports that some of the children have perished in the cold." The psychological strains were also telling, he said: "The people don't know how long they still have to hold out as refugees. This hopeless situation is causing some people to consider emigration while they don't actually want to leave."

The archbishop also said that a visit to the region by Pope Francis was in consideration: "The Holy Father is expected in Iraq both by the Church and the political powers, and even by non-Christians such as the Shiite leadership. I am impressed how great the consensus is concerning the figure of the Pope."

Foreign ministers from around the world are meeting in London to discuss how to take on Islamic State. Britain's foreign secretary Philip Hammond told Radio 4's Today programme that it would be "months" before the Iraqi army was ready to take on the jihadists. "We are renewing and regenerating the Iraqi security forces – re-equipping them, retraining them, reorganising them – but it will be months yet before they are ready to start significant combat operations against Isil."

"They will be able to do it, the question is when they will be ready to start that process," he added.

Referring to Islamic State by its Arabic acronym Daesh, Iraq's Prime Minister Haider al-Abadi told David Cameron: "Iraq is facing a real crisis, a fiscal crisis and other crises in facing Daesh. We are waging a war in Iraq and war is very costly.

"We have soldiers' boots on the ground – I think we are the only country who have boots on the ground to fight Daesh.

"Iraqi people have sacrificed their lives in facing Daesh. We have reversed, some time ago, the advances of Daesh and we are very keen to push them back from the whole of Iraq.

"But this is a fight of the world and Daesh must be eliminated from the region and from the whole of the world."