"I am not a quitter and there's a long-term job to be done. I am doing what I believe is important for the sake of the country," she told reporters at the start of her three-day visit to China.
May has been under mounting pressure from all sides, with some of her party MPs questioning her leadership and the Opposition demanding more details of a leaked economic study which warns of disastrous consequences in the wake of Britain's exit from the European Union (EU).
She sought to play down the leaked impact assessments drafted by UK civil servants, showing a hit to the UK economy in all end-state scenarios with the EU post-Brexit.
She said, "It would be wrong to describe this as 'the Brexit impact assessment'. There is analysis being done. This is very preliminary.
More From This Section
The leaked study, published by the 'Buzzfeed' news website on Monday, suggested that in three different scenarios the UK economy would grow more slowly than it would if it stayed in the European Union.
The Labour party had called for the report to be fully released since its existence is now public knowledge and several MPs of the ruling Conservatives also joined ranks with the Opposition demanding that the material be made public.
"If the House decides it wants to see the provisional analysis then we will abide by the will of the House," a Downing Street spokesperson said.
Labour's shadow Brexit secretary, Keir Starmer, hailed the move as a "significant win for democracy".
UK Brexit minister Robin Walker told MPs a copy of the report would be given to Hilary Benn, the Labour chairman of the Commons Brexit Committee, and a confidential reading room will be provided for other MPs and peers to view the material on a "confidential basis".
Meanwhile, May announced new education links with China during her visit to boost post-Brexit trade and investment.
She is leading a 50-strong trade delegation of UK-based companies, including Tata Motors-owned Jaguar Land Rover (JLR), and is expected to raise concerns from UK industry about the over-production of steel by China.
The British premier has also refused to endorse China's Belt and Road Initiative, over concerns that the infrastructure projects under the initiative lack financial transparency and rely heavily on Chinese contractors.