Theresa May has become the first Conservative Prime Minister to visit Argentina - and the only one to visit its capital - since Margaret Thatcher's Falklands war.

Mrs May is in Buenos Aires for the G20 summit of industrialised nations on Friday and Saturday, hosted by Argentinian president Mauricio Macri.

Tonight she conducted a private meeting with Macri and vowed that Britain will continue to defend the South Atlantic archipelago, to which Argentina also lay claim.

British Prime Minister Theresa May and Argentine President Mauricio Macri sit for a bilateral on the sidelines of the G20 summit in Buenos Aires, Argentina, 30 November 2018

May is welcomed by Argentina's President Macri. The Group of Twenty (G20) Summit brings together the heads of State or Government of the 20 largest economies and takes place from November 30 to December 1 2018

Britain's Prime Minister Theresa May and Argentina's President Mauricio Macri talk during the G20 Leader's Summit at the Costa Salguero Center in Buenos Aires

Macri has softened rhetoric on the islands, known in Argentina as Las Malvinas, compared to his predecessor Cristina Kirchner.

But Mrs May still wanted to make clear that Britain had not been lulled into a false sense of security and would send forces to the Falklands if need be.

The Prime Minister said: 'I am talking to president Macri about opportunities for trade, but our position on the sovereignty of the Falklands hasn't changed – and will not change.'

Margaret Thatcher meets personnel aboard the HMS Antrim in January 1983 during her five-day visit to the Falkand Islands

Lady Thatcher on a visit to the Falkland Islands in June 1992, ten years after the Falklands war

The meeting comes 36 years after the 1982 war, and this week the two governments announced a new agreement on an additional air link between South America and the Falkland Islands, via Argentina.

The British government issued a statement saying that the new flight, as well as annual bilateral air services discussions, was part of the recognition 'that building closer links represents a shared goal.'

'The additional air link will greatly benefit the people of the Falkland Islands and support their economic development.

'It will also engender wider engagement and provide economic benefit for the region,' the statement said.

Jorge Faurie, the Argentinian foreign minister, said the recent establishment of more flights to the disputed islands was a positive development.

Regarding Mrs May's visit, he said: 'Dialogue must be maintained.'

Relations between the two countries have thawed since Macri took over as President from Cristina Kirchner in 2015 and toned down rhetoric regarding the disputed Falklands (Las Malvinas)

'We are not withdrawing our historic claim,' he added. 'The focus of this opportunity is in the reestablishment of trust.'

In the meantime, Mrs May will push the case for reform of the World Trade Organization at the G20 summit, including increasing transparency, updating dispute settlement processes and promoting trade in services and digital alongside goods.

'We will take our independent seat at the WTO next year when we leave the European Union and we do see the need for reform,' she told reporters on the plane.

Mrs May is only the second British prime minister to travel to Argentina and the first to visit Buenos Aires. Labour's Tony Blair briefly visited Argentina in 2001.

Britain is expected to announce that it will create a post of trade envoy to Buenos Aires following talks between May and Argentine President Mauricio Macri.