China and the U.S. struck new climate, military, trade and visa agreements during two days of talks at the Asia-Pacific Economic Cooperation summit, as presidents Barack Obama and Xi Jinping made significant strides in improving an often-tense relationship.

Xi and Obama reached two agreements designed to avert military confrontations in Asia, one on notifying each other of major activities, such as military exercises, and the other on rules of behavior for encounters at sea and in the air, according to the Wall Street Journal.

The agreements are rare signs of progress on core issues in the rocky relationship. The U.S. is trying to consolidate influence in Asia, while Beijing is determined to make China the region’s pre-eminent military and economic power.

APEC, which also includes Japan, South Korea and Australia, is the first major international gathering in China since Xi took power. The presence of world leaders gives Beijing a platform to lobby for a bigger leadership role, The Associated Press noted.

The military agreements reflected the surprising progress made on defense ties since the Sunnylands summit in California in June 2013. The need for better military relations has been underscored by China’s efforts to enforce contested maritime claims across the South China and East China seas.

“It’s incredibly important that we avoid inadvertent escalation and that we don’t find ourselves again having an accidental circumstance lead into something that could precipitate a conflict,” the Journal quoted Ben Rhodes, a U.S. deputy national security adviser, as saying.

The agreements, called “military-to-military confidence-building mechanisms” by the White House, are part of a broader effort to persuade the Chinese military to adopt international norms, and to encourage other Asian nations to strike similar agreements, defense analysts said.

The notification mechanism covers policy and strategy developments, as well as the observation of military exercises and activities, the Wall Street Journal reported. The rules of behavior include details on encounters between naval surface vessels, according to a White House statement.

The U.S. would prioritize developing details on air-to-air encounters, and creating a mechanism to inform each other of ballistic missile launches, the statement said.

China has long opposed a military-encounters agreement with the U.S. on the grounds that it implied an adversarial relationship like that between the U.S. and the former Soviet Union, the Journal noted.

That has changed in the last year as both sides have recognized that they can’t reconcile their interpretations of international law on maritime issues, but also can’t allow unintended military encounters to derail their relationship.

“We need a third way between our disagreements,” Peter Dutton, director of the China Maritime Studies Institute at the U.S. Naval War College, told the Journal. “The U.S.-China relationship at sea is too important to leave encounters to chance.”

China, the U.S. and 19 other countries with navies that operate in the Western Pacific agreed in April to establish the region’s first code of conduct for unplanned encounters between military ships and aircraft in international waters.

But China hasn’t always observed that in areas that it sees as territorial waters and that the U.S. regards as international waters. In August, the Pentagon accused Chinese jet fighters of flying dangerously close to U.S. surveillance aircraft over the South China Sea.

In recent meetings, Chinese military commanders have privately assured U.S. officials that such close encounters shouldn’t happen again, according to the people familiar with the discussions.

At the Beijing meetings this week, Xi took another important step to reduce tensions in the region, agreeing to meet with Japanese Prime Minister Shinzo Abe after two years of confrontation over islands in the East China Sea, called Diaoyu in Chinese and Senkaku in Japanese.