By Catherine Davis BBC Central Asia correspondent in Kyrgyzstan

Kyrgyzstan and China are starting two days of joint anti-terrorist exercises along their border.

A spokesman for the Kyrgyz defence ministry said the aim was to co-ordinate operations both sides of the border in the event of terrorists trying to cross.

The region's states have long warned of the dangers posed by terrorism and religious extremism and planned ways to combat it.

But some observers believe China also wants to increase its profile in the region now US troops are based there.

It is the first time such manoeuvres have been staged by members of the Shanghai Co-operation Organisation.

Challenging task

The training is taking place in remote mountainous terrain.

Kyrgyz defence officials say the plan is not for troops to physically cross the border but to improve co-ordination on both sides.

It is not a simple task.

Overcoming the language barrier is just one of the challenges faced.

Three Central Asian states share a border with China thousands of kilometres long.

There are well-established trade links and new border crossings too. Political and military contacts have grown over the past decade.

Small countries like Kyrgyzstan are very aware of the vast presence to their east - likewise of their former master, Russia.

Their policy is to seek a balance, to have good relations with various powers.

That has become more obvious in recent months now American troops are based in Kyrgyzstan itself.

China's motives

China, meanwhile, has a large and restive population in its western province.

It is anxious to prevent it gaining support from fellow Muslims in Central Asia.

Some observers argue China is continuing to pursue its interests here just as before.

Others believe there are signs Beijing is concerned that Central Asia's closer relations with Washington could reduce its influence in the region.

For them, these exercises on the Chinese-Kyrgyz border also have geo-political importance.