Earlier in the day, the UK Supreme Court declared unlawful the removal of asylum seekers to Rwanda and therefore rejected the Home Office's appeal to revise a similar decision of a lower court.
Sunak held talks with Rwandan President Paul Kagame, and the two leaders agreed to continue their cooperation on migration issues despite the court's ruling, the UK government said.
"We will clear the remaining barriers and flights will be heading off in the spring as planned," Sunak was quoted as saying by UK media.
The UK prime minister also pledged to introduce emergency legislation to make sure that the Rwanda plan is not blocked again.
The UK government is working on a new migration agreement with Rwanda, Sunak said. A cabinet spokesman added later that the document would be presented for review in the coming days. Newly-appointed UK Interior Minister James Cleverly said the agreement would be upgraded to a treaty level.
Undocumented migration has been a pressing issue for the UK for years and intensified after the country left the European Union in 2020. In April 2022, the UK and Rwanda signed a migration agreement, stipulating that people recognized by the UK government as undocumented migrants or asylum seekers will be deported to Rwanda for the processing of their documents, obtaining asylum, and relocation.