KAOSHIUNG, Taiwan -- Taiwan and the Philippines are taking steps to boost maritime ties after decades of distance, as rising pressure from Chinese vessels makes a case for closer cooperation at sea.

Taiwan's Coast Guard is planning a visit to the Philippines next October, which would be the first known call since 1974, the year before Manila switched diplomatic recognition to the People's Republic of China. Taiwan recently donated a patrol vessel to Manila, and there are reports that a decommissioned Taiwanese navy ship is to be transferred as well, although the defense ministry has declined to comment on the speculation.

Individually, both Taipei and Manila have been intensifying their pushback against Chinese maritime incursions, combining diplomatic protests with more assertive frontline interceptions.

This month, Taiwan's Coast Guard chased away four Chinese quasi-military ships and fired its water cannons at a Chinese fishing boat that authorities said failed to respond to warnings. A Chinese government spokesman last Wednesday said that Taiwan, which China claims as its territory, would have to "bear the consequences" of the action, without elaborating.

Over the last two weeks, the Philippines has driven away Chinese maritime militia and research vessels. Manila and Beijing have long been at odds over their overlapping territorial claims in the South China Sea, with the Chinese side rejecting a 2016 international arbitration decision that rejected its position.

A high-ranking Taiwan government official involved in ties with the Philippines told Nikkei Asia that "as close neighbors in the first island chain, both nations face China's expansionist, coercive and aggressive behavior," referring to a strategic line of Pacific archipelagos that also includes Japan's Okinawa.

"As China attempts to assert its false maritime claims through the use of both military and non-military assets, such as coast guard or research vessels, it's important for Taiwan and the Philippines to engage in closer coordination and exchange relevant experiences on maritime security," the official said on condition of anonymity.

Of growing concern are Chinese maritime "law enforcement" operations to the east of Taiwan which started ostensibly in response to sea boundary talks Japan and the Philippines agreed to launch over the summer. The maneuvers have raised fears in Taipei and beyond about rising risks of accidental collisions or confrontations.

Despite having territorial friction with China in common, Taiwan and the Philippines have not always been on the same page. Back in 2013, relations suffered a rupture when a Philippine Coast Guard vessel fired on a Taiwanese fishing boat, killing a crew member. But maritime and other engagement has come a long way since.

"This is crucial in countering China's incremental expansionism," the Taiwan official said of the budding cooperation.

Nikkei Asia reported last month on plans for the opening of a new Taiwan quasi-diplomatic mission in Cebu in the Philippines, later confirmed by the Taiwanese foreign minister. Collectively, the moves represent progress in broadening Taiwan's ties with a neighbor analysts see as the most important player in the theater after the U.S. and Japan when it comes to deterring China's military ambitions.

At a recent Taiwan Foreign Correspondents' Club briefing, U.S. security expert Oriana Skylar Mastro said Taiwan's efforts to strengthen economic and political relations with Manila are "really important."

"From a military operational perspective, the only two places within combat radius of Taiwan are the northern Philippines and the southwest islands of Japan," said Mastro, a center fellow at Stanford University's Freeman Spogli Institute for International Studies. "Any other operations that any entity does from anywhere else, you get more and more vulnerable because you rely on what we call enablers, things like tankers, space and networks that are very hard to protect." Taiwan Coast Guard patrol vessels are stationed in Keelung, Taiwan, on Dec. 30. There are signs of budding maritime cooperation between Taipei and Manila.

Citing research data at Stanford analyzing every access-based and overflight arrangement the U.S. has worldwide, she said what matters in a conflict is the degree of interoperability. "The more connectivity there is between Taiwan and the Philippines, [the more likely] the Philippines will allow operations off their soil in the defense of Taiwan," Mastro said.

At a public forum last month, the deputy secretary-general of Taiwan's National Security Council, Lii Wen, said that "Taiwan has been learning from the Philippines' success on assertive transparency."

The Philippines makes a point of publicizing information about actions by Chinese vessels in the South China Sea. "Many countries in the region are increasingly recognizing the importance of disclosing China's coercive maritime behavior in a clear and timely way," Lii said. "It is important for more countries to adopt transparency initiatives together, so that China cannot pressure and bully the few countries that speak up." Moves like the coast guard visits and ship transfers are "small in material terms, but they matter as signals," said Dan Blumenthal, a former senior director for China, Taiwan and Mongolia at the U.S. Department of Defense.

"Coast guards are the front line of gray-zone pressure in the waters around both Taiwan and the Philippines, and regular, visible exchanges normalize cooperation between two neighbors that have historically kept their maritime relationship quiet," said Blumenthal, now with the American Enterprise Institute. "A first port visit in years, if it happens, would show both sides are willing to build habits of working together." Blumenthal said a first priority is to ensure Taipei and Manila have a reliable channel for managing incidents, especially involving fishermen in their overlapping EEZs, or exclusive economic zones, so that any mishap does not become a political crisis. He also urged practical cooperation on search and rescue, disaster response, maritime domain awareness and joint training.

Still, efforts to balance diplomatic sensitivities continue. Last month, the Philippines' Department of Foreign Affairs reiterated its commitment to its "One China policy," while emphasizing that this "does not preclude the Philippines from pursuing economic, cultural and functional cooperation with Taiwan." The donation of Taiwan's patrol vessel was handled through a nongovernmental organization called the We Protect Our Seas Foundation (WPS Foundation). It said in a statement that the gift gives the Philippine Coast Guard an additional platform for maritime civilian operations.