The UK will begin the process of ratifying the global climate change agreement within weeks, Theresa May said, as she used her first speech to the United Nations to stress that the UK remained a global player following the Brexit vote.
Mrs May said the UK would complete the process of ratifying the Paris agreement by the end of the year.
The Prime Minister told the gathering of world leaders in New York that the UK remained a "confident, strong and dependable partner internationally".
She said: "We will continue to play our part in the international effort against climate change.
"And in a demonstration of our commitment to the agreement reached in Paris, the UK will start its domestic procedures to enable ratification of the Paris agreement, and complete these before the end of the year."
The command paper leading to the ratification will be laid in Parliament after it returns from the conference recess next month.
Mrs May said when Britons backed Brexit "they did not vote to turn inwards or walk away from any of our partners in the world".
"Faced with challenges like migration, a desire for greater control of their country, and a mounting sense that globalisation is leaving working people behind, they demanded a politics that is more in touch with their concerns; and bold action to address them."
Mrs May stressed that the UK was committed to the target of spending 0.7% of gross national income on overseas aid and the Nato commitment to spend 2% of GDP on defence.
The UN general assembly has been dominated by the migration crisis and Mrs May has set out the principles guiding her approach - including that refugees should claim asylum in the first safe country they reach and nations have a right to protect their borders.
She also called for a better distinction between genuine refugees and economic migrants.
She said: "By ensuring a managed and controlled international migration response - and at the same time investing to tackle the underlying drivers of displacement and migration at source - we can reject isolationism and xenophobia, achieving better outcomes for all of our citizens – and particularly for the most vulnerable."
Mrs May said the world's leaders must acknowledge the concerns felt around the world about the pace of globalisation.
"We must never forget that we stand here, at this United Nations, as servants of the men and women that we represent back at home," she said.
"And as we do so, we must recognise that for too many of those men and women the increasing pace of globalisation has left them feeling left behind.
"Faced with challenges like migration, a desire for greater control of their country, and a mounting sense that globalisation is leaving working people behind, they demanded a politics that is more in touch with their concerns; and bold action to address them."
A senior UK source said Mrs May's address, her first major speech on foreign policy, showed her view that "the more we do earlier on overseas, the better we can protect people at home".
Her belief was that "foreign policy should be about how best do you serve British interests," the source said.