UK to increase nuclear stockpile
The Guardian and The Sun said in their online editions that the country would look to raise the number of warheads from 180 to 260 by the middle of the decade.
Both dailies said details were contained in a leak they had seen of the government's long-awaited Integrated Review, due to be published on Tuesday.
The review is also said to state clearly that Russia under President Vladimir Putin poses an "active threat" but describes China as providing a more "systemic challenge".
London has increasingly locked horns with both Moscow and Beijing in recent years, on issues ranging from espionage and cyber-attacks to human rights.
Britain's Trident nuclear programme is a thorny political issue domestically, with repeated calls for it to be scrapped, given global moves towards disarmament after the end of the Cold War.
Opponents for its abolition include the main opposition Labour party and the Scottish National Party (SNP). Britain's nuclear submarine fleet is based in the west of Scotland.
The Campaign for Nuclear Disarmament (CND) called the reports "shocking" given the pressures of the global coronavirus pandemic and climate change.
"We don't want any more nuclear weapons. In fact, we don't want any," it added.
She said it was "irresponsible, dangerous and violates international law", adding: "This is toxic masculinity on display."
- Strategic 'tilt' -
Prime Minister Boris Johnson is due to set out the conclusions of the year-long review -- entitled "Global Britain in a Competitive Age -- to parliament on Tuesday.
His Downing Street office billed the 100-page report as the government's "most comprehensive articulation of a foreign policy and national security approach" in decades.
It comes as London looks to reposition itself post-Brexit, rebranding itself "Global Britain" and eyeing new opportunities beyond the European Union.
Johnson's office said the recommendations included a strategic "tilt" towards the Indo-Pacific region, given its increasing importance in global geopolitics.
Britain has already applied for partner status at the Association of Southeast Asian Nations (ASEAN), while Johnson is due to make his first post-EU visit to India in April.
Other key areas the review will address include plans for the military to adopt cutting-edge technologies such as drones and artificial intelligence.
There will also be a new focus on space and cyber, as well as a revamp of Britain's ability to respond to security threats with the creation of a White House-style situation room.
A new Counter-Terrorism Operations Centre is also proposed.
The review is said to be a response to a changing world in which Britain "cannot rely solely on an increasingly outdated international system".
It will stress the continuing importance of alliances, including with NATO, but set out a new foreign policy of "increased international activism... to shape a more open international order in which democracies flourish".