China has delivered two frigates to Pakistan’s navy, completing a four-warship deal inked in 2018, Chinese media reported, amid deepening military cooperation between the two nations in one of the world’s most complex geopolitical regions.

The vessels - two Type 054A frigates - will be used to safeguard the seas of the China-Pakistan economic corridor (CPEC), state-backed Chinese newspaper Global Times reported late on Wednesday.

CPEC is an ambitious infrastructure project that links Xinjiang in west China to Pakistan aimed at offering an alternative transportation route in the future for goods including gas. Part of the network is Pakistan’s Gwadar port, located on a key waterway in the Arabian Sea.

Economic and military ties between the two neighbours have deepened against a shifting geopolitical backdrop, evident from Pakistan’s increasing military procurement from China and joint military exercises to safeguard assets and trade routes. For China, Pakistan and its access to the Arabian Sea is key in the event of a maritime blockade in the Strait of Malacca.

China delivered the first batch of six J-10 fighter jets to Pakistan in March last year. Eight Hangor Class submarines that Pakistan ordered from China are expected to be delivered before 2028.

Earlier this week, China’s defence minister told Pakistan’s navy chief that their militaries, including their navies, should “expand into new fields of cooperation” to bolster their capability in safeguarding regional security.

“The prospects for cooperation between the two sides, in my opinion, is getting stronger and stronger,” Song Zhongping, a military commentator with Phoenix TV, told Reuters.

In South Asia, China’s ties with India, with whom Pakistan has frosty relations, have deteriorated in recent years, and the withdrawal of U.S. troops in nearby Afghanistan has raised geopolitical uncertainty in the region, pushing China and Pakistan to seek a stronger alliance.

“Maintaining the peace and stability of South Asia fits with both countries’ actual interests,” Song said.