US Secretary of State Mike Pompeo will head to Britain next week to reaffirm the US "special relationship" with the country ahead of its exit from the European Union, the State Department announced Friday.

Pompeo will travel to London on January 29, meeting with Prime Minister Boris Johnson and Foreign Secretary Dominic Raab to "discuss ways to broaden and deepen trade ties" after Brexit at the end of the month.

From there he will head on to Ukraine -- the country at the heart of the ongoing impeachment trial of President Donald Trump who is accused of pressuring his Ukrainian counterpart to investigate a White House rival.

Johnson is cultivating Britain's relations with Washington in a bid to offset the potential damage of withdrawal from the EU.

But the British government on Friday rebuked the US for refusing to extradite a diplomat's wife charged over a car crash that killed a British teenager, with Raab calling it a "denial of justice."

Pompeo had rejected the extradition request, Britain said.

US Secretary of State Mike Pompeo is heading to Britain ahead of Brexit
US Secretary of State Mike Pompeo is heading to Britain ahead of Brexit AFP / Ezequiel BECERRA

The case of Anne Sacoolas has been a recent thorn in London's ties with Washington.

Harry Dunn, 19, died in August when his motorcycle collided with a car driven by Sacoolas on the wrong side of the road in Britain. Trump has called the crash a "terrible accident."

In Kiev, Pompeo will meet President Volodymyr Zelensky, who is at the center of Trump's impeachment trial.

The Democratic prosecution team at the Senate trial has alleged Trump flagrantly tried to force Zelensky to help him tarnish his possible 2020 reelection challenger, former vice president Joe Biden.

Trump appears set for exoneration by the Republican-held upper chamber.

Key to the impeachment scandal is a July 25 telephone call in which Trump pushed Zelensky to announce a graft investigation of Biden.

Trump is accused of withholding nearly $400 million in military aid for Ukraine's war against Russian-backed separatists, and refusing Zelensky a White House meeting unless he opened the probe.