Australians should view a growing U.S. military presence as a “natural evolution” as the strategic alliance between the two countries comes to grips with rising tensions in the South China Sea, Royal Australian Air Force chief Leo Davies said.

“We’ve got a U.S. plane coming in pretty much every day” to operate routine exercises and missions in Australia, Davies told reporters in Canberra on Tuesday. The nation provides an opportunity for the U.S. to conduct long-range exercises, which are proving difficult to conduct elsewhere in the world, he said.

Australia, which hosts U.S. Marines and military exercises in its remote northern regions, is seen as a partner in President Barack Obama’s economic and military “rebalance” to Asia, with Prime Minister Malcolm Turnbull last month echoing U.S. calls for China to refrain from militarizing reefs it has reclaimed in the South China Sea.

The strengthening of the alliance comes as Australia ramps up military spending, with the defense budget to surge from 32.4 billion Australian dollars ($24.3 billion) in 2016-17 to A$58.7 billion in 2025-26. Defense Minister Marise Payne told a conference Tuesday that the government had increased its order of P-8A Poseidon surveillance aircraft by four to a total of 12. The aircraft, to replace aging AP-3C Orion planes, will begin to be delivered in 2017 and are expected to become operational by 2021.

U.S. Pacific Command chief Harry Harris told a Senate committee in Washington last month said that he relied “heavily” on Australia for its advanced military capabilities, while Pacific Air Forces chief Gen. Lori Robinson said last week that the U.S. is continuing talks with Australia to have B-1 bombers rotate through the northern port of Darwin.

Australia has held talks with regional nations, including Singapore, the Philippines and Vietnam to ensure so-called freedom of navigation exercises in the South China Sea are maintained, Davies said. Militarization in the region “has accelerated at a level that has been difficult to” stay in step with, he said. The U.S. began the such operations in October as a way to challenge China’s claims to more than 80 percent of one of the world’s busiest shipping lanes.

“This is about an international approach to international law and how that’s applied,” Davies said. “From an airman’s point of view, I will abide by the rules of the air, we will fly in the airspace we are entitled to, we will put our diplomatic clearances in for the places we need to cross into and we will operate as we have done for the past 30-plus years in the South China Sea.”

Under President Xi Jinping, China has reclaimed more than 3,000 acres (1,200 hectares) of land on seven features in the Spratly archipelago in the past two years, adding airstrips, lighthouses and port facilities to better project influence over the waterway. The nation sparked new questions about its intentions in the South China Sea after surface-to-air missiles and radar facilities were detected last month on Woody Island, part of the Paracel Islands northwest of the Spratlys.

“Our patrols have not changed,” Davies said. “We are still mixing our Gateway patrols through the northern Indian Ocean and South China Sea.” Davies said he didn’t want Australia’s navy to be in a position where it thought “because that atoll now looks different, I have to go in a different direction” than on previous exercises, he said.

In Kuala Lumpur, Malaysian Defense Minister Hishammuddin Hussein said Monday that he will meet his Australian counterpart next week to discuss China’s military buildup in the South China Sea and hold talks with fellow claimants the Philippines and Vietnam.

Beijing is feeling public pressure at home to show it can protect its claims to the waters after the U.S. freedom of navigation operations.

Hishammuddin said he would meet Payne to ensure efforts are made to “hold China to their promise of not placing military assets in the area.”

“If the reports we’ve received from various sources regarding the buildup and placement of military assets in the Spratlys are true — this forces us in a pushback against China,” Hishammuddin told reporters.

In September, Chinese President Xi Jinping said China had no intention to militarize its outposts in the Spratly Islands.

The director of U.S. national intelligence, James Clapper, said in a letter in February that China’s land reclamation and construction work on the islands had established infrastructure needed “to project military capabilities in the South China Sea beyond that which is required for point defense of its outposts.”

The 10-member Association of Southeast Asian Nations (ASEAN) said last month it was “seriously concerned” over developments in the disputed waters.

Hishammuddin said he would also meet with authorities in Vietnam and the Philippines as, if reports on China’s military expansion were true, Malaysia “cannot act alone in stopping the aggressive actions.”

“We need the support of other ASEAN countries, and I will continue to (seek that support),” Hishammuddin said. “This is important for us to maintain balance, and to curb the actions by superpowers, whether it is China or the United States.”