John Bolton, U.S. President Donald Trump's national security adviser, arrived in London on Sunday for talks at which he is expected to urge Britain to toughen its stance on Iran and Chinese telecommunications firm Huawei.

As the United Kingdom prepares to leave the European Union on Oct. 31, its biggest geopolitical shift since World War II, many diplomats expect London to become increasingly reliant on the United States.

Bolton's two days of talks on Monday and Tuesday, to include a heavy focus on Brexit, reflect the Trump White House's attempts to solidify ties with the new British government of Prime Minister Boris Johnson after Trump's strained relationship with former Prime Minister Theresa May.