The United States and the Philippines will sign a 10-year defense agreement Monday, officials said, one of the clearest signs yet of renewed American engagement in the region at a time when tensions between China and its neighbors have been rising.

The announcement — the biggest policy achievement to come out of President Obama’s week-long trip to Asia — is likely to generate criticism from Chinese officials, who have made it clear they oppose a heightened U.S. presence in the area. But the pact may reassure several Asian countries embroiled in territorial disputes with China, especially in the South China Sea. It also gives the United States greater flexibility to respond to threats and natural disasters in the region.

“This is the most significant defense agreement that we have concluded with the Philippines in decades,” said Evan Medeiros, the National Security Council’s senior director for Asian affairs, adding that the United States wants “a constructive relationship with China” but also is determined to pursue policies based on its strategic objectives and those of its allies. “And as those threats evolve, the nature of our alliances and security partnerships will evolve as well, whether it’s Japan or South Korea,” Medeiros said.

At least four other countries in the region — Brunei, Malaysia, Taiwan and Vietnam — also are feuding with China over control of parts of the South China Sea. Those territorial claims have both security and economic implications, because the country that controls those areas can access fisheries and underwater oil and gas deposits.

Rommel Banlaoi, executive director of the Philippine Institute for Peace, Violence and Terrorism Research, wrote in an e-mail that the defense cooperation agreement will not only increase the United States’ presence in the region but also will “justify an increase of U.S. military assistance to the Philippines as a major non-NATO ally.”

President Obama is in Asia for a four-country tour to promote commerce and trade as part of his administration's so-called "Asia pivot." But with rising tensions in the region, what does his relationship with Japan, South Korea and China look like? (Julie Percha/The Washington Post)

“The Philippines can use this agreement as a leverage against China’s military and para-military presence in the Spratlys,” Banlaoi wrote, referring to an archipelago of largely uninhabited islands claimed by China and several other countries.

The defense pact had been under negotiation for about eight months. U.S. officials had anticipated that it would be signed during Obama’s visit, but that had not been a certainty until Sunday.

The accord does not provide for establishing U.S. bases but will entail moving American ships and planes to the Philippines more frequently as well as engaging in more training exercises with the country’s forces.

Michael Green, senior vice president for Asia and Japan chair at the Center for Strategic and International Studies, said the arrangement is not just about defending the Philippines. It is also about better dispersing American forces in the region.

“U.S. bases are too concentrated in a few places in Asia, which is not good when you’re trying to build relationships, but it’s also not good when there are more ballistic missiles aimed at you,” Green said. “And so it’s about having a lot more access across the whole region, but not bases, which are expensive and politically risky for the U.S. and for the Philippines.”

‘A renewal of the bond’

The new agreement amounts to a historic reversal for the Philippines, which forced the United States to withdraw from the 60,000-acre Subic Bay naval base in 1992. That break terminated an American military presence dating to when the United States wrested the Philippines from Spain in 1898.

Philippine politicians had celebrated the U.S. withdrawal. Then-Sen. Agapito Aquino, the uncle of the country’s current president, called it “the dawn of our nation’s birth.”

Since then, however, China has become more aggressive about seeking control of land in the region, which it says wound up unfairly in foreign hands. Taylor Fravel, a political science professor at the Massachusetts Institute of Technology, noted in an interview that the expulsion of U.S. forces “must be [the Philippines’] greatest geopolitical regret.”

A decade ago, China occupied Mischief Reef, a part of the Kalayaan Island Group that the Philippines views as its territory; at this point China has claimed sovereignty over almost 85 percent of waters in the South China Sea. In response to the incident at Mischief Reef, the Philippine government negotiated a visiting-forces agreement with the United States that was adopted in 1999.

In the aftermath of Typhoon Haiyan in November, Filipinos feel even more warmly toward the U.S. armed forces, which played a critical role in the recovery effort. Alfred Romualdez, mayor of the hard-hit city of Tacloban, called the relationship “a renewal of the bond, especially for the next generation.”

“Here were the Americans, who were the first ones to come, and operated the airport,” he said, adding that the assistance allowed relief materials to be distributed more widely to rural areas surrounding the city.

Avoiding armed conflict

The Philippine government has confronted China on some of its moves in the South China Sea, arguing before the Permanent Court of Arbitration in the Netherlands that a contested shoal — called Ayungin in the Philippines and Ren’ai Reef in China — lies within its exclusive economic zone.

Ben Rhodes, deputy U.S. national security adviser for security communications, told a reporter that “this isn’t an agreement designed at resolving maritime disputes, with any particular maritime dispute as a focal point of why we did this.”

But he added that the closer security relationship could discourage any provocative activities that could lead to armed conflict. “The presence of the United States in the Asia Pacific has been a stabilizing force for a long time,” Rhodes said.

The announcement of the pact came on the same day that Malaysia endorsed — for the first time — the idea of resolving territorial and maritime disputes in the area through international arbitration that uses the Law of the Sea Treaty as its framework.

Obama and Malaysian Prime Minister Najib Razak highlighted in a joint statement “the importance of all parties concerned avoiding the use of force, intimidation, or coercion, and exercising self-restraint in the conduct of activities.”

While the administration is also pursuing closer economic and cultural ties with Asia, enhanced security cooperation remains the most visible part of its effort to “rebalance” the relationship. The administration is on track to have a 60-40 ratio of Navy and Air Force assets in the Pacific compared with the Atlantic by the end of the decade, instead of an even split.

And at every stop on this four-country tour, Obama has emphasized the idea that the U.S. government is committed to helping its allies in the face of external threats, whether they are North Korean nuclear weapons or future moves by China to take control of islands at the center of a territorial dispute with Japan.

In an effort to defuse any possible conflict with China on the defense accord with the Philippines, senior U.S. officials privately briefed the Chinese government on their plans before Obama left Washington last week for Asia.

Rhodes noted that the details of the agreement would be worked out under the Mutual Defense Treaty of 1951, which “gives us a rock-solid commitment to the security of the Philippines.”

Once those details are settled, U.S. ships may be headed back to the very place they were expelled from more than two decades ago.

“There are a variety of facilities on the table,” Rhodes said. “Subic Bay could be one of them.”