U.S. Secretary of State Mike Pompeo is flying to London on Wednesday following U.K. Prime Minister Boris Johnson's green light to Chinese tech giant Huawei allowing the company to help build the U.K.'s 5G network, which received criticism from Washington.

Britain decided Tuesday to allow Huawei to help build aspects of its new high-speed mobile network – but said it would exclude it from "core" parts of the new network.

However, the U.S. objects to the contract due to concerns over the potential for cyberespionage and has threatened to cut off security.

The decision is awkward for Jonson's government, as he risks the fury of one of Britain's closest allies at just the moment it really needs Trump's administration to quickly strike a trade deal after Brexit. PM Johnson has been touting the prospects of a big new trade deal with the U.S. that can fill the void of Britain's departure from the EU.

Britain is also keen to avoid insulting China, which it also needs for future trade.

Pompeo's meetings with Foreign Secretary Dominic Raab and Johnson on Wednesday and Thursday threaten to become a damage limitation exercise for the "special relationship." The U.S. Secretary of State has been doing his best to convince Johnson that allowing the Chinese tech giant to help build Britain's next-generation 5G network poses a serious long-term security threat.

London argues, however, that preventing Huawei's role would have cost the U.K. tens of billions of pounds while causing a delay in implementing the 5G technology by at least two years.

"The United States is disappointed by the U.K.'s decision," a senior administration official said in a statement after Johnson's green light.

Meanwhile, Johnson has been pushing Washington to send back the wife of a U.S. diplomat who is using the cover of diplomatic immunity to avoid prosecution over the death of a teenager in a road accident in England last August. The United States rejected Anne Sacoolas's extradition to Britain last week.

"We feel this amounts to a denial of justice," Raab said in response. "The U.K. would have acted differently if this had been a U.K. diplomat serving in the U.S."

Disagreements about Iran and a U.S. prosecutor's complaint that Prince Andrew was stonewalling an FBI investigation into the late sex offender Jeffrey Epstein only add to the layers of tensions.

Johnson may now simply be hoping "there are no precipitous statements from the U.S. saying 'that's it, this love affair is at an end,'" said Ian Bond of London's Center for European Reform.

Bond pointed out that U.S. officials had repeatedly warned how Huawei's inclusion in Britain's 5G rollout could force Washington to stop sharing intelligence with London. "It would probably be safe to say that the British have not taken those (threats) very seriously and now is the moment we will find out whether they should have taken them more seriously or not," Bond told AFP.

Talking trade

Britain will cap Huawei's share of the 5G market to about a third in a bid to create space for new companies to step in. However, Johnson's decision still tests the limits of his well-publicized friendship with the mercurial White House chief.

Trump has been a big fan of both Johnson and Brexit, having dangled the promise of a new trade deal with Britain by as early as the end of the year. Those talks can formally get underway once Brexit takes effect on Friday.

Any comprehensive agreement would need ratification in Congress and none is expected when most Americans' attention is focused on the heated presidential election campaign; but a bare-bones deal that lays the foundation for future talks could work in both Trump and Johnson's political favor.

Some cybersecurity experts said Johnson's decision to keep Huawei away from the "core" elements of the 5G network should appease Washington's technical concerns. "Essentially what they've done is limit Huawei from large parts of the network," said the Royal United Services Institute think tank's cyber research chief James Sullivan, adding, "You would hope this would blow over in the next few weeks."