LONDON (Reuters) - 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.

U.S. National Security Adviser John Bolton walks to give an interview to Fox News outside of the White House in Washington, U.S. July 31, 2019. REUTERS/Leah Millis

As the United Kingdom prepares to leave the European Union on Oct. 31, its biggest geopolitical shift since World War Two, 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.

Bolton is expected to urge British officials to align policy on Iran more closely with that of Washington, which has pressured Tehran with ever-tightening sanctions after Trump withdrew the United States from the Iran nuclear deal.

Britain has so far backed the European Union in sticking with the nuclear accord, known as the Joint Comprehensive Plan of Action, but the seizure of a British oil tanker in the Strait of Hormuz has put pressure on London to consider a tougher stance.

British marines seized an Iranian vessel, which is suspected of smuggling oil to Syria, off the coast of Gibraltar on July 4. This month, Britain joined the United States in a maritime security mission in the Gulf to protect merchant vessels.

A senior Trump administration official said Bolton’s argument to the British will be that it would help add pressure on Iran if London would declare the JCPOA dead but that such a decision was not expected soon.

Trump has also pushed Britain to get tougher on China’s Huawei out of concern its next-generation 5G technology represents a national security risk. Washington wants its allies, including Britain, to avoid using equipment from Huawei.

Under former PM May, the British government decided in principle to give Huawei limited access to non-core parts of the 5G network, but the senior U.S. official said Bolton hoped to find a friendlier audience on the topic from the Johnson government. A final British decision has not yet been taken.

Bolton plans to argue that Huawei is an arm of the Chinese government and that its hardware could be used to monitor communications that go through its system.

Trump and New York-born Johnson have spoken frequently on the phone since the new prime minister took power and Trump wants to seal a U.S.-British free trade agreement in order to help cushion Britain when it exits the European Union.

The two leaders are to meet later this month at the G7 summit in Biarritz, France.

Bolton, who met last week in Washington with British Foreign Secretary Dominic Raab, is to have lunch on Monday with Britain’s cabinet secretary, Mark Sedwill, and later meet at No. 10 Downing Street with Edward Lister, who is Johnson’s chief strategic adviser.

Later in the day, Bolton will meet Sajid Javid, Johnson’s new finance minister.

On Tuesday, Bolton is due to meet Liz Truss, Britain’s international trade secretary, and Ben Wallace, the new defense secretary, as well as Steve Barclay, the minister for exiting the European Union, among other officials.