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MANILA, July 22 (Reuters) - U.S. Secretary of State Marco Rubio and his Chinese counterpart Wang Yi discussed on Wednesday a planned visit by Chinese President Xi Jinping to the United States in September on the sidelines of an Asian meeting that saw expressions of concern over a war with Iran and tensions in the South China Sea.

Rubio said he had extensive discussions with Wang about the need to lay the groundwork for a "very positive" visit by President Xi, and that their task was to manage the major differences between the two countries and ensure they did not get out of control.

An official summary from China showed that Wang urged the United States to "respect China's core interests... effectively manage differences and disagreements and address China's legitimate concerns" and described the meeting as "practical, positive and constructive".

The Chinese Foreign Ministry said in a statement that Wang and Rubio agreed to "prepare well for the next stage of high-level communication."

The ASEAN meeting in Manila comes amid escalating tensions between the United States and Iran, and at a time when tensions are rising between Beijing and the Philippines, a close US ally, over an incident in the South China Sea on Monday that prompted both countries to recall their ambassadors.

During his meeting with the foreign ministers of the League of Nations, who expressed their deep concern about the Middle East war, Rubio placed full responsibility for it on Iran.

He said, "The problem we face at the moment is that they do not seem serious about the talks... If they are serious, we will reciprocate. If they are not, we will do what is necessary to protect our interests, and the interests of our allies as well."

He stressed that Iran cannot be allowed to control the Strait of Hormuz, because that could set a dangerous precedent for other parts of the world.

* "A geopolitical weapon"

Rubio's remarks come in the wake of an opinion piece published by Philippine media on Tuesday, in which he criticized Beijing's behavior in the South China Sea, warning of "new and grave threats" if "those waters fall under the control of a power willing to use trade as a geopolitical weapon."

Beijing claims sovereignty over almost the entire South China Sea through a line on its maps that overlaps with the exclusive economic zones of Brunei, Indonesia, Malaysia, the Philippines and Vietnam, and this has sparked long-standing disputes over a large number of islands and maritime areas.

Australian Foreign Minister Penny Wang described a clash on Monday between the Chinese coast guard and Philippine navy personnel in the South China Sea as dangerous and destabilizing.

She added to reporters, "Countries in the region have a choice about how we all respond to this."

Chinese Foreign Ministry spokesman Lin Jian responded by saying that Australia has no right to interfere in the South China Sea and that Beijing "calls on the countries concerned to stop stirring up tension and inciting confrontation."

Canadian Foreign Minister Anita Anand described the escalating tensions affecting maritime navigation as "worrying," adding in an interview with Reuters that it is essential to reach a negotiated settlement in the Middle East and to protect freedom of navigation through waterways such as the Strait of Hormuz.

Disagreements between the Philippines and China have intensified in recent years, as Manila adopts a more hardline stance on the South China Sea, while simultaneously seeking to strengthen defense ties with the United States, as well as Australia and Japan.

The U.S. State Department said in a fact sheet that the United States increased foreign military financing to $100 million for fiscal year 2026 and is providing an additional $9 million to expand the Philippine Coast Guard pier on Palawan Island "to enhance the Philippine maritime law enforcement presence and support operations in the South China Sea."

Russian Foreign Minister Sergey Lavrov confirmed he will meet with Rubio in Manila on Thursday. Rubio said he will discuss the war in Ukraine with Lavrov, emphasizing that Washington is seeking to play a constructive role in ending the conflict.

Rubio also met with his counterparts from India, Australia and Japan, a four-way grouping that Beijing criticized, describing it as resembling Cold War-era alliances.

Rubio's meeting with Wang, which lasted about 90 minutes, came amid a fragile truce between the world's two largest economies. However, these issues could be complicated by President Donald Trump's accusations that China interfered in the US presidential election, accusations which Beijing has denied.

Rubio said these allegations were not discussed and that they talked about trade, Taiwan and potential areas of cooperation before Xi's visit to Washington.

The Chinese Foreign Ministry said Wang "articulated China's official position on a series of recent negative statements and actions by the US side" and urged the United States to abide by the "One China" principle.