YEREVAN, Sep 18 (AFP) - US House Speaker Nancy Pelosi arrived Saturday in Armenia, days after the Caucasus country's deadly border clashes with Azerbaijan jeopardised Western efforts to broker lasting peace between the arch foes.

The worst clashes since Yerevan's 2020 war with Baku erupted on Tuesday, claiming the lives of 215 people, before hostilities ended on Thursday after international mediation.

Pelosi said her visit "is a powerful symbol of the United States firm commitment to a peaceful, prosperous and democratic Armenia, and a stable and secure Caucasus region."

She is the highest-ranking US official to travel to Armenia since the tiny impoverished nation's 1991 independence from the Soviet Union.

The three-day visit "will play a big role in ensuring our security," Armenian parliament Speaker, Alen Simonyan, told journalists ahead of her arrival.

Armenia and Azerbaijan have fought two wars -- in 2020 and in the 1990s -- over the contested Nagorno-Karabakh region, Azerbaijan's Armenian-populated enclave.

Together with France and Russia, the US co-chairs the Minsk Group of mediators, which had led decades-long peace talks between Baku and Yerevan under the OSCE aegis.

"We will convey the strong and ongoing support of the United States, as an OSCE Minsk Chair and longtime friend to Armenia, for a lasting settlement to the conflict in Nagorno-Karabakh," Pelosi said in a statement.

The latest escalation came as Armenia's closest ally Moscow is distracted by its nearly seven-month war in Ukraine.

Analysts have said the hostilities have largely undone Western efforts to bring Baku and Yerevan closer to a peace deal.

With Moscow increasingly isolated on the world stage following its February invasion of Ukraine, the European Union had taken a lead role in mediating the Armenia-Azerbaijan normalisation process.

The six weeks of fighting in 2020 claimed the lives of more than 6,500 troops from both sides and ended with a Russian-brokered ceasefire.

Under the deal, Armenia ceded swathes of territory it had controlled for decades, and Moscow deployed about 2,000 Russian peacekeepers to oversee the fragile truce.

Ethnic Armenian separatists in Nagorno-Karabakh broke away from Azerbaijan when the Soviet Union collapsed in 1991. The ensuing conflict claimed around 30,000 lives.