(CNN) -- British Prime Minister Boris Johnson is receiving "standard oxygen treatment" and is breathing without assistance, his spokesperson said Tuesday, a day after being transferred to intensive care with coronavirus.
Johnson's condition is stable and he "remains in good spirits," his spokesperson said. He has not required required invasive or non-invasive ventilation and does not have pneumonia.
The Foreign Secretary Dominic Raab would chair meetings of the National Security Council if any was needed while he is deputizing for the Prime Minister. Raab and the UK's Cabinet have the authority and ability to respond in the PM's absence on military action, the spokesperson said.
Raab, 46, is running the country from the Foreign and Commonwealth Office with the support of government officials, but cannot hire and fire ministers. Decisions relating to Covid-19 would be taken in the usual way through the daily morning meeting, chaired by Raab, and other ministerial groupings.
Buckingham Palace and the Queen have been regularly updated on the PM's condition. The Cabinet Secretary and Principal Private Secretary will maintain contact with the palace on the Prime Minister's behalf, Downing Street said. But the weekly audiences with the Queen would not continue for the time being.
The spokesperson said that despite the lack of a formal succession procedure in the UK, there was an established order of ministerial precedence, with the top finance minister, Rishi Sunak following Raab. The "letters of last resort," sealed documents written by the Prime Minister to ballistic missile submarine commanders in cases of a nuclear attack, still stand. "The Prime Minister remains the Prime Minister," the spokesperson said.
The UK lockdown will remain in place with the government "focussed on stopping the spread of the infection." The spokesperson said that if there were evidence that more needed to be done to slow the rate of transmission, "we would be prepared to do that."
US Donald Trump said at a Monday news conference that his administration had been in contact with Johnson's doctors. The spokesperson said the government was "grateful for all of the warm wishes the PM has received overnight" and "confident he is receiving the best care from the NHS. Any treatment he receives is a matter for his doctors."
Cabinet Office minister Michael Gove told BBC Radio 4's Today program earlier that Johnson was "receiving the very best care" at St. Thomas' Hospital in London, after being taken into intensive care at 7 p.m. local time (2 p.m. ET) on Monday.
"And of course, one of the reasons for being in intensive care is to make sure that whatever support the medical team consider to be appropriate can be provided," Gove said.
Gove later said he was self-isolating at home because a member of his family was showing coronavirus symptoms. Gove said on Twitter that he was not displaying any symptoms and was continuing to work. He's the latest in a long line of British government ministers and advisers to be forced into isolation.
Johnson's hospitalization has highlighted the lack of a formal line of succession in the UK government. Johnson, 55, nominated the Foreign Secretary, Raab, who also holds the title of First Secretary of State, to deputize for him "where necessary." But there is no official deputy recognized by UK law or the country's largely unwritten constitution.
Few formal powers are invested specifically in the UK prime minister and key decisions are taken collectively by the Cabinet or its sub-committees. Many statutory powers are held by individual secretaries of state. But in recent decades, holders of the UK's top political office have adopted a more presidential style, and the sweeping nature of the ruling Conservative Party's most recent election victory was attributed to Johnson's personal appeal with voters.
"The Prime Minister has a team around him who ensure the work of government goes on," Gove told the BBC. He said Johnson had a "stripped-back diary" last week to make sure he could follow the medical advice of his doctors.
Gove confirmed that Raab was now in charge of seeing through Johnson's plan to tackle the novel coronavirus. "Dominic [Raab] takes on the responsibilities of chairing the various meetings the PM would've chaired but we're all working together to implement the plan that the PM has set out," he said.
But Gove sidestepped a question about who held the "nuclear codes," saying he would not discuss national security issues.
Conservative MP Tobias Ellwood, who chairs the House of Commons defense select committee, tweeted good wishes to Johnson but added: "It is important to have 100% clarity as to where responsibility for UK national security decisions now lies. We must anticipate adversaries attempting to exploit any perceived weakness."
Johnson was taken to hospital on Sunday evening. At the time, Downing Street said the decision was a precaution because he continued to suffer from a cough and a fever ten days after testing positive for the coronavirus. But his condition deteriorated on Monday, Downing Street said, and he was moved to the intensive care unit at St. Thomas' Hospital.
Gove told Sky News on Tuesday morning that Cabinet ministers were not told about the Prime Minister's deteriorating condition until nearly an hour after Johnson was taken into intensive care.
Asked whether the government had been up front with the public about Johnson's condition, and whether the Cabinet had been taken by surprise, he replied: "Yes we were. The [daily coronavirus] briefing that was given at 5 o'clock was given at a time when we didn't know about the deterioration in the Prime Minister's condition."
"We were informed subsequently. The Prime Minister was admitted to intensive care at 7 o'clock, and that information wasn't given to us in government -- to those in the cabinet -- until just before 8 o'clock."
The coronavirus has hit the top of the British government hard. The Health Secretary, Matt Hancock, said on March 27 that he had the virus, on the same day that chief medical officer, Chris Whitty, announced that he would begin self-isolation after displaying Covid-19 symptoms. Neil Ferguson, a top UK government adviser on the virus, said on March 18 he believed he had been infected. Various other senior government ministers and advisers have been forced to self-isolate.
Politicians around the world sent best wishes for the Prime Minister's recovery.
UK Treasurer Rishi Sunak said on Twitter that his thoughts were with Johnson and his pregnant fiancée, Carrie Symonds. "I know he'll be getting the best care possible and will come out of this even stronger," he said.
Symonds has also experienced Covid-19 symptoms but said over the weekend she was "on the mend."
The leader of the UK's House of Commons, Lindsay Hoyle, said: "I know the thoughts and prayers of everyone across the House are with the Prime Minister and his family right now. We all wish him a speedy recovery."
Keir Starmer, the newly elected leader of the UK's main opposition Labour Party leader, tweeted: "Terribly sad news. All the country's thoughts are with the Prime Minister and his family during this incredibly difficult time."
Former Prime Minister Theresa May, who was replaced by Johnson in the country's Brexit crisis, wrote on Twitter said her "thoughts and prayers" were with Johnson and his family. "This horrific virus does not discriminate," she added.
French President Emmanuel Macron sent his "support to Boris Johnson, to his family and to the British people at this difficult moment," wishing him a "speedy recovery at this testing time."
Irish leader Leo Varadkar, who has returned to work as a doctor during the outbreak, tweeted that Johnson was "in our thoughts" on Monday night and wished him "a rapid return to health."
Nicola Sturgeon, Scotland's First Minister, said everyone's thoughts at her Scottish National Party were "with the Prime Minister and his family right now" while Japan's Prime Minister Shinzo Abe said his thoughts and prayers were with his "dear friend," adding: "The people of Japan stand with the British people at this difficult time."
President Donald Trump said on Monday: "We're very saddened to hear that he was taken into intensive care this a little while ago. He's been a really good friend. He's been really something very special. Strong. Resolute."
"We've contacted all of Boris's doctors, and we'll see what is going to take place, but they are ready to go," Trump continued. "When you are brought into intensive care that gets very, very serious."
"We are working with London with respect to Boris Johnson."
CNN's Angela Dewan also contributed reporting.