BEIJING (AP) - The Chinese president visits Central Asia this week amid concerns that a U.S. troop withdrawal from Afghanistan could mean a destabilizing exodus of foreign radical fighters from the war zone to homelands closer to China's borders.

BEIJING (AP) The Chinese president visits Central Asia this week amid concerns that a U.S. troop withdrawal from Afghanistan could mean a destabilizing exodus of foreign radical fighters from the war zone to homelands closer to China's borders.

With the pullout deadline just 16 months away, China's leaders share widespread concerns that Kabul's own forces won't be able to maintain security or that foreign fighters who were focused on fighting U.S. troops will now head elsewhere, including other fragile Central Asian nations or even northwestern China.

Xi Jinping's trip, starting Tuesday, also is seen as an attempt to shore up China's trade and relationships with governments in the region, extending Beijing's influence in an area traditionally dominated by Russia.

"It's vitally important for China's development to have prosperity, peace and stability in Central Asia," said Li Xin, a Russia and Central Asia specialist at the Shanghai Institute of Foreign Studies. "The worry is the withdrawal of U.S. troops will have a spillover effect."

Xi's visits to Turkmenistan, Kazakhstan, Uzbekistan and Kyrgyzstan are his first to the region since taking office as president in March. He'll end the trip in Kyrgyzstan where he will attend the annual summit of the Shanghai Cooperation Organization, a Russian- and Chinese-dominated grouping that Beijing hopes will boost its diplomatic influence in the region to better match its already considerable economic clout.

China surged past the EU as Central Asia's biggest trading partner in 2010, and did $40 billion in commerce with the five-nation bloc in 2011. Much of that comes in the form of oil and gas, with two pipelines carrying supplies to China from Turkmenistan and Kazakhstan.

China, for its part, provides economic assistance and much-needed investment to meet the desperate infrastructure needs of the region and its 66 million people, helming projects such as the 2.3-kilometer (1.4-mile) Shar-Shar Tunnel linking Tajikistan to China.

Ensuring energy supplies and protecting its investment rank high among China's reasons for wanting to ensure Central Asian stability. Even more important is its desire to block support for anti-government radicals among the Turkic Muslim Uighur ethnic group that is native to China's vast northwestern region of Xinjiang and whose members share religious, cultural and linguistic ties to the people of Central Asia.

Uighurs have been fighting a low-level insurgency in China, fired by resentment of ethnic Han Chinese dominance and a form of imported radical Islam that cuts against the grain of their region's traditional moderate sufi beliefs. Their hardline Islamic sentiments are shared by Central Asian groups such as the Islamic Movement of Uzbekistan and the Islamic Revival Party of Tajikistan, some of which preach violent overthrow of their governments.

This year has been particularly bloody in Xinjiang, with scores killed and hundreds arrested in raids, attacks and riots. It isn't clear what is fueling the spike in bloodshed, but authorities have shown their unease by boosting security in the region.

"Beijing is consumed by insecurity," said Andrew Scobell, a senior political scientist at the RAND Corporation in Arlington, Virginia. "China's greatest fear is linkups between internal challenges and external threats, notably the Uighur diaspora that spills across national borders."

China believes strong economies and markets in neighboring states are a key to stability in Xinjiang, said Raffaello Pantucci, a terrorism expert at the Royal United Services Institute think tank in England.

"The government believes that economic development is at the heart of resolving the region's ethnic tensions, and in order for the region to succeed it needs to have a prosperous region adjacent to trade with," Pantucci said.

China has invested much of its aspirations for bringing stability to Central Asia in the Shanghai Cooperation Organization, pushing to expand the grouping's activities to include joint anti-terrorism exercises and intelligence sharing. Russia favors its own Collective Security Treaty Organization, but Beijing has nonetheless managed to involve Moscow in SCO as an alternative to U.S. influence in region following the 2014 drawdown.

China has been conflicted over the U.S. presence in Central Asia. It has argued against a long-term American footprint in the region and urged Kyrgyzstan to close the Manas Transit Center air base, which supplies troops in Afghanistan. Beijing sees such facilities as part of a strategy to hem in China's growing power and influence.

At the same time, China has relied on U.S. troops to create the conditions for pursuing its own interests in Afghanistan, including plans to extract vast amounts of copper and coal. Beijing signed a strategic partnership last summer with the war-torn country and in September sent its top security official to Kabul, the highest level Chinese official to visit in 46 years. Beijing also announced it would train 300 Afghan police officers as part of its continuing, low-key aid program for the nation.

Now that U.S. troops are leaving, Beijing has been hesitant to make new commitments, possibly because it is waiting to see how stable the Kabul government will be, analysts say.

"China considers Afghanistan to be the epicenter of Islamic extremism in the region," Scobell said.

"China has a high degree of concern about instability in Afghanistan and considerable alarm that the draw-down could spill over into adjacent countries, including western China," he said.