LONDON, Sept 7, 2022 (BSS/AFP) - UK Prime Minister Liz Truss and US President Joe Biden "agreed on the importance of protecting" peace in Northern Ireland, in a phone call Tuesday hours after Truss became Britain's new leader.

Truss, who replaces Boris Johnson, told Biden that she also looked forward to "working closely" with Washington "as leaders of free democracies to tackle shared challenges," a Downing Street spokeswoman said.

They include "the extreme economic problems unleashed by (Russian President) Putin's war," she added in a readout of their call.

It comes amid reported concerns in the United States over Truss, after her one-year tenure as foreign secretary saw post-Brexit tensions in Northern Ireland surface and strain Britain's ties with Brussels, Dublin and Washington.

In that previous role, Truss spearheaded legislation in Britain's parliament that would unilaterally override parts of a UK-EU trade pact for Northern Ireland, which the bloc and Irish government vehemently oppose.

Biden, who has Irish roots, has been critical of the Brexit policy pursued by Britain under Johnson, and was seen to share a lukewarm relationship with the former British leader.

Biden had warned ahead of his 2020 election that if Brexit damaged the 1998 Good Friday Agreement he would not consent to a UK-US trade deal. That agreement ended 30 years of violence in Northern Ireland.

A trade agreement between London and Washington is currently seen as a distant prospect.

However, defence ties between the two trans-Atlantic allies have strengthened in recent years, with a new partnership involving Australia -- dubbed AUKUS -- agreed last year.

In their phone call Tuesday, Truss and Biden "agreed to build on those links, including by furthering our deep defence alliance through NATO and AUKUS".

"The leaders reinforced their commitment to strengthening global liberty, tackling the risks posed by autocracies and ensuring Putin fails in Ukraine," the Downing Street spokeswoman added.

The White House for its part said the two leaders discussed their "shared commitment" to Belfast agreement, as well as "the importance of reaching a negotiated agreement with the European Union on the Northern Ireland Protocol."

In its readout of the call, the White House also said Truss and Biden addressed "the challenges posed by China (and) preventing Iran from ever acquiring a nuclear weapon."

They also reaffirmed "the special relationship" between Britain and the United States and expressed their readiness to further deepen the ties, according to the readout.