Theresa May has assured Gulf leaders a post-Brexit Britain would not abandon the Middle East, adding that Islamic State's "days are numbered".
Attending a summit of the Gulf Co-operation Council in Bahrain, the Prime Minister also announced a new bid to tackle people trafficking, modern slavery, and online exploitation of children.
May told Gulf leaders the UK was taking "a leap forwards" with Brexit as a "passionate" advocate for free trade.
Referring to Islamic State as Daesh, the PM said: "Today, UK servicemen and women are putting their lives on the line at the heart of the international mission against Daesh in Iraq and Syria.
"We are making progress. And as we are seeing with the current operations in Mosul, the days of Daesh as an occupying force are numbered."
The Prime Minister used the address to strongly back the Iran nuclear deal after intense criticism of the agreement by US President-elect Donald Trump.
May is only the third Western leader, and first woman, to be invited to the summit, and was referred to as "her majesty" and "her highness" in the English translation of summit proceedings.