The United States has unveiled a new defense strategy that would slim down its military and rebalance it toward the Asia-Pacific region, away from Europe and the Middle East.

Washington officials said the new strategy would have no impact on the U.S. forces stationed in South Korea. They reaffirmed the U.S. commitment to maintain peace on the Korean Peninsula and deter any provocations by North Korea.

Yet policymakers in Seoul need to analyze the U.S. policy change carefully as it comes at a time when security instability on the peninsula has sharply increased following the death of North Korean leader Kim Jong-il.

The new U.S. defense strategy, unveiled by President Barak Obama on Thursday, addresses Washington’s need to reorder its military priorities as the decade-old war against terrorism is nearing an end. The war in Iraq ended with the completion of troop withdrawals last month.

The reshaping of the U.S. military was also prompted by severe budget constraints. To bring the federal deficit under control, the Obama administration agreed with Congress to scale back defense spending by more than $1 trillion over the next 10 years.

While a detailed troop reduction plan is still not available, Washington officials suggested the U.S. Army and Marine Corps would cut personnel levels by 10 to 15 percent over the next decade.

According to reports, the U.S. Army is expected to cut its forces from the current 565,000 to 490,000, while the Marine Corps is likely to reduce troop numbers from 201,000 to around 195,000.

Despite these reductions, defense officials in Washington and Seoul reassured there would be no drawdown of U.S. Forces Korea, which has around 28,000 soldiers.

Their reassurances were based on Washington’s shift in focus to the Asia-Pacific region. Obama stressed the U.S. would increase its military presence in the Asia-Pacific, saying that “budget cuts will not come at the expense of that critical region.”

The rebalancing toward the Asia-Pacific is aimed at countering China’s move to expand its influence in the Pacific. In recent years, Beijing has deployed a new generation of weapons to prevent U.S. naval and air forces projecting power into the Far East.

Given Korea’s strategic location, Washington is unlikely to reduce the size of USFK for the time being. But this does not rule out the possibility of the U.S. deploying some of the USFK troops to other international missions under the doctrine of “strategic flexibility.”

In 2009 Washington sent one of the two Apache attack helicopter battalions stationed in Korea to Iraq. The powerful unit did not return to Korea after the war ended.

The planned troop retrenchment is likely to increase the need for Washington to mobilize USFK troops to deal with conflicts in other parts of the world. This could create a hole in Seoul’s defense posture.

A slimmed-down U.S. military also raises a flag with Seoul as it could limit Washington’s capability to provide contingency reinforcements to South Korea in case of a North Korean invasion.

At the Pentagon press briefing, U.S. Secretary of Defense Leon Panetta referred to the possibility of the U.S. facing a land war in Korea and threats in the Straits of Hormuz at the same time.

“We have the capability to deal with those kinds of threats, to be able to confront them and to be able to win,” Panetta said. But if Washington can retain such a capability even after troop reductions, it would not have abandoned its long-held “two-war strategy.”

The two-war strategy calls for an ability to fight and win two conventional wars simultaneously. Washington has jettisoned this strategy and adopted a more realistic “one-plus strategy,” which is aimed at winning one major war while still being able to deter enemies in another conflict.

In case North Korea invades the South, a contingency plan, coded Operation Plan 5027, is activated, requiring the U.S. to dispatch nearly 700,000 troops, 160 destroyers and 2,000 airplanes from its bases in the U.S., Japan and Guam.

But if U.S. troops are scaled back as planned, it is unclear how Washington will implement the plan. Hence it is necessary for officials in Seoul and Washington to resolve this uncertainty. Otherwise, security concerns will heighten here.

Seoul also needs to accelerate its defense capability reinforcement scheme, which is geared to the planned takeover of the wartime operation control from the U.S. in December 2015.