17 May 2011 Last updated at 09:08 ET

Pakistani Prime Minister Yousuf Raza Gilani has arrived in China on a four-day visit to commemorate 60 years of diplomatic ties between the countries.

Earlier, he described China as Pakistan's "best friend".

Although the visit was planned long ago, correspondents say it is especially timely for Islamabad because of strains with the US over the killing of Osama Bin Laden.

China is one of Pakistan's staunchest allies and trading partners.

"We appreciate that in all difficult circumstances, China stood with Pakistan. Therefore we call China a true friend and a time-tested and all-weather friend," Mr Gilani told China's official Xinhua news agency.

"We are proud to have China as our best and most trusted friend, and China will always find Pakistan standing beside it at all times," he said in an interview released on Tuesday.

The BBC's Jill McGivering says this latest display of warmth seems designed to reflect Pakistan's appreciation for China's uncompromising support in recent days.

Any divisions between Pakistan and the United States could be an opportunity for China - Pakistan is desperate for foreign investment, especially in infrastructure, one of China's specialities, our correspondent adds.

Diplomatic balance
Mr Gilani's first stop is Shanghai. On Wednesday he is due to speak at a cultural forum in the eastern city of Suzhou. He will then travel to Beijing, where he will meet Chinese leaders, including President Hu Jintao and Premier Wen Jiabao.

The two sides are expected to sign a series of agreements and discuss how they can fight extremism.

Trade between the two countries is increasing significantly. It reached $8.6bn (£5.3bn) last year, an increase of nearly 30% compared with 2009.

China is now believed to be Pakistan's biggest supplier of military equipment, providing surface-to-air missiles, warships and fighter jets.

Last week Pakistan opened a new nuclear reactor in Punjab, built with Chinese help. At least two more are planned.

Chinese officials and state media have hinted that they will use Mr Gilani's visit to portray Beijing as a steadfast and reliable partner in contrast to Washington, described in one editorial as a fickle and demanding interloper.

"US opinion has not only failed to criticise its own unilateralism in this action [against Bin Laden] violating Pakistani territorial sovereignty, it has vilified Pakistan as a scapegoat for its own rough going in its war against terror," an editorial said on Monday in the overseas edition of the People's Daily, China's main official newspaper.

Damian Grammaticas
BBC News, Beijing
Ever since US special forces killed Osama Bin Laden deep inside Pakistan there has been a crisis in relations. Mr Gilani's visit is a chance to send a pretty powerful signal - that Pakistan has an alternative backer in Beijing should America push Islamabad too far.

Pakistan feels dwarfed and threatened by India and China is a useful counterbalance. But it's important to get this in perspective. Both China and Pakistan still have more significant links with America than with each other.

China's relationship with the US is by far its most significant diplomatic relationship, dwarfing any ties with Islamabad. Pakistan receives billions of dollars in US aid and, despite the tensions, both Islamabad and Washington are enmeshed in a joint fight against extremists.

Beijing has no desire to become dragged into Pakistan's internal problems. That could lead the Taleban or al-Qaeda to target China, which is the last thing Beijing wants.

So neither Pakistan nor China are about to ditch America and embrace each other. Instead what we are seeing is a China that is expanding its influence and a shifting, but delicate diplomatic balance between these three powers.

http://www.bbc.co.uk/news/world-south-asia-13418957