Britain’s Foreign Secretary Dominic Raab said the threat of Iran keeps him awake at night.
In an interview on BBC Radio 4 on Tuesday, Mr Raab said the UK faced a “range of threats” that include cyberwarfare, terrorism and nuclear proliferation.
Asked what keeps him awake at night, Mr Raab said a nuclear Iran was one of his primary concerns. Britain is trying to work with Tehran to avoid the country developing its own nuclear arsenal, he said.
“We’re trying to engage with Iran. We must never see Iran get a nuclear weapon,” he said.
“We’ve got other states and the risks of nuclear proliferation, not just nuclear, but chemical right the way through to terrorist groups, criminal gangs using warped technology ... cyber-attacks that target critical national infrastructure,” he added.
His comments came as the government prepared to publish its Integrated Review document outlining Britain's future foreign and defence policy for the next decade.
The document sets out how Britain should expand its influence among democratic nations in the Indo-Pacific region, while preserving strong ties with the United States. It is the biggest review of British foreign and defence policy since the end of the Cold War three decades ago.
Prime Minister Boris Johnson wants Britain to be at the forefront of a reinvigorated, rules-based international order based on co-operation and free trade.
"I am profoundly optimistic about the UK’s place in the world and our ability to seize the opportunities ahead," Mr Johnson will say in a statement to parliament.
Britain holds two influential roles this year; hosting the first post-pandemic G7 summit in June, and the COP26 climate conference in November.
The 100-page document, due at 1130 GMT, will be closely scrutinised for concrete measures showing how the government will deliver on Mr Johnson's rhetoric at a time when the country is struggling to come to terms with the realities of Brexit and the Covid-19 pandemic.
Relations with China, which is on course to become the world's largest economy, have frayed badly over issues including Beijing's handling of former British colony Hong Kong, increasingly vocal criticism of China's state-subsidised industry and security concerns related to Chinese investment in Britain.
The Queen Elizabeth aircraft carrier's long-planned deployment is expected to raise military tension in the South China Sea.
Mr Raab earlier told Sky News that Britain would like to have a positive relationship with China, but not at the expense of upholding its values, which requires a "calibrated approach" towards Beijing.
A statement previewing Tuesday's Integrated Review listed "the importance of our relationship with the US," as well as the defence of democracy and human rights and safety from terrorism as fundamental components of British policy.
Britain is seeking a trade deal with the US and reassurance over where it ranks in President Joe Biden’s international priorities.