"She is battling hard for our country and no-one is better placed to ensure we deliver on the British people's decision to leave the European Union". And she insisted a general election would not be "in the national interest".
Speculation about Mr Javid's possible leadership ambitions was fuelled by an interview in the Spectator magazine in which he set out a broad-ranging vision for the Conservatives as the party which can "make a real difference to you as an individual in your life".
This evening, May told Tory MPs she will not be leading the party into the next general election, Amber Rudd said.
In a bid to win over wavering lawmakers, May indicated she would step down before the next election, due in 2022.
The British pound, which has lost 25 cents against the USA dollar since the 2016 referendum, was down 0.5 percent at $1.2501, falling after a Sky news reporter said a vote of confidence in May's leadership was about to be triggered.
Another Tory legislator, Nick Boles, tweeted: "She was unambiguous". Now the PM's own party may sack her.
A leadership election "would not change the fundamentals of the negotiation or the parliamentary arithmetic", she said.
He resigned his Cabinet position in July in protest over May's Brexit plan, which he denounced as too soft and has since then eviscerated her exit strategy in regular columns for the Daily Telegraph newspaper.
However, her motives are derived from her desire to stop Brexit.
Opposition lawmakers expressed astonishment and outrage at the Conservative civil war erupting in the middle of the fraught Brexit process.
"A change in leadership will put our country's future at risk and create uncertainty when we can least afford it", she said outside 10 Downing Street. "At one of the most pivotal moments for the United Kingdom economy in decades, it is unacceptable that Westminster politicians have chosen to focus on themselves, rather than on the needs of the country", said Adam Marshall, director-general of the British Chambers of Commerce. "As time is running out, we will also discuss our preparedness for a no-deal scenario".
Earlier Sir Graham Brady, the chairman of the 1922 backbench committee, released a statement confirming the threshold of 48 signatures - 15 per cent of the total number of Tory MPs - "has been exceeded".
She must now fly to Brussels on Thursday to appeal to her fellow European Union leaders to offer Britain what she told MPs must be a "legally binding" commitment that the Irish backstop will be temporary.
Several top members of her cabinet quickly rallied to her support.
If May survived the motion, no second one can be taken by party members for another year.
A day after abruptly pulling the vote, Mrs May rushed to The Hague for breakfast with Dutch Prime Minister Mark Rutte, then to Berlin to meet Chancellor Merkel, followed by a trip to Brussels.
May could be toppled if 158 of her 315 lawmakers vote against her.
Backbencher Anna Soubry said it was time for the prime minister to face down hardline Brexiters on the right of her party. May's authority has been badly eroded along and it's doubtful she'll be able to secure a new Brexit deal that would win enough support in Parliament.
But Penny Mordaunt, Portsmouth North MP and worldwide development secretary, posted on Twitter and said: 'The Prime Minister has my full support, not least because she has always done what she firmly believes is in the national interest.
European Union leaders tried to stay out of the fray.