Britain is to take in an extra 3,000 vulnerable child refugees in what the Government called the "largest resettlement programme in the world" for children from the Middle East and North Africa.
The move is aimed at saving children at risk of being exploited, forced into early marriage or abused.
Some of the rescued children will arrive with their families or carers, the Home Office has announced.
Several hundred of the children will be resettled in the first year of the programme, with the remainder arriving by 2020.
The drive, which is being advised by the United Nations High Commissioner for Refugees (UNHCR), goes beyond just targeting unaccompanied children, and provides support and resettlement to children defined as "at risk".
The initiative, which the Government says is the largest resettlement effort aimed specifically at children at risk from the Middle East and North Africa region, is in addition to Britain's commitment to resettle 20,000 Syrian refugees under the Vulnerable Persons Resettlement Scheme (VPRS).
The VPRS has already resettled over 1,000 Syrian refugees, over half of them children, and is set to resettle several thousand Syrian children over the next four years.
Immigration Minister James Brokenshire said: "The UK Government is committed to providing life-saving support and assistance to the vulnerable children who have been unjustly impacted by this ongoing humanitarian crisis.
"We have always been clear that the vast majority of vulnerable children are better off remaining in host countries in the region so they can be reunited with surviving family members. However, there are exceptional circumstances in which it is in a child's best interests to be resettled in the UK.
"We have engaged with a number of NGOs, including the UNHCR on the best way to provide protection to refugee children and ensure their welfare and safety remain at the heart of every decision made. This new scheme compliments our ongoing work within Europe to assist vulnerable migrant children. This includes the £10 million Refugee Children Fund to identify and support vulnerable children and strengthen child protection and family reunification systems."
UNHCR representative to the UK, Gonzalo Vargas Llosa, said: "Today's launch of the UK Government's resettlement scheme for refugee children at risk is an important contribution to UNHCR's continuing efforts to address the global protection needs of refugee children, including through resettlement and other pathways for admission.
"We welcome the scheme's focus on children at risk, including unaccompanied and separated children, and the UK's commitment to upholding the principles of child protection and the child's best interest, in implementing the programme."
The Government has also announced its initial offer of support for the implementation of the EU-Turkey migration agreement in Greece to prevent illegal crossings from Turkey.
The UK will offer 75 expert personnel to help with processing and administration of migrants in reception centres.
This is intended to ensure that vulnerable people, including children, are identified and can access asylum systems as quickly as possible, while other migrants will be returned to Turkey in accordance with the EU-Turkey deal.
The children at risk resettlement scheme will be reviewed after two years.