MANILA, Sept 8 (Reuters) - Australia and the Philippines on Friday agreed to hold annual defence ministers' meetings as the two nations upgraded bilateral ties to a strategic partnership amid rising security challenges in the region, including in the South China Sea.

Australian Prime Minister Anthony Albanese signed a strategic partnership agreement with Philippine President Ferdinand Marcos Jr. during his trip to Manila, the first visit by an Australian leader in 20 years.

"Australia is working with our partners including the Philippines to shape a region where sovereignty is upheld," Albanese said in a joint press conference with Marcos after holding bilateral talks

Marcos said their countries' close ties were "terribly important".

The Philippines last month held military exercises near the South China Sea with Australia, its second-largest partner in defence security. It is also one of only two bilateral partners with whom the Philippines has a Status of Visiting Forces Agreement, which allows two countries to undertake joint exercises, high-level visits, dialogues and exchanges.

Australia has discussed pursuing joint navy patrols in the resource-rich waterway.

Albanese threw his support behind a 2016 arbitral ruling on the South China Sea that invalidated China's expansive claims in the strategic waterway where about $3 trillion worth of ship-borne trade passes annually.

"Australia supports the 2016 South China Sea arbitral award. That is final and binding. And it is important that it be upheld going forward," Albanese said.

The Philippines, Malaysia, Vietnam, Brunei and Taiwan have claims to certain areas of the South China Sea. Most of Australia's trade also goes through the South China Sea.

Albanese confirmed on Thursday he will visit China later this year, the first visit by an Australian leader since 2016.