Factbox: Ties between China and Pakistan

Pakistan, facing a crisis in relations with the United States, has embarked on a charm offensive with China this week, keen to portray its "all-weather friend" as an alternative ally to Washington.

Here are some facts about ties between China and Pakistan:

"ALL-WEATHER" PARTNERS

* China and Pakistan call each other "all-weather friends" and their close ties have been underpinned by long-standing wariness of their common neighbor, India, and a desire to hedge against U.S. influence across the region.

* After the United States killed Osama bin Laden -- the mastermind of the September 11, 2001, attacks -- in Pakistan on May 2, China called the event a "progressive development" but also defended the Pakistani government, which has been criticized in the United States for failing to find bin Laden, if not harboring him.

CONVENTIONAL ARMS, NUCLEAR POWER, PORT ACCESS

* China has been Pakistan's biggest supplier of conventional arms, according to the Stockholm International Peace Research Institute's database, and many analysts believe China supported Pakistan's nuclear weapons program in past decades.

* China has helped Pakistan build its main nuclear power generation facility at Chashma in Punjab province, where a second, 330 MW unit started last week, and it has plans to build two more there, despite international misgivings about risks to nuclear safety and the integrity of non-proliferation rules.

* Last year, the China National Nuclear Corp said it was also in talks about building a separate 1-gigawatt atomic plant in Pakistan.

* China has helped build the deep-sea Gwadar port on Pakistan's Arabian Sea coast, partly with a view to opening up an energy and trade corridor from the Gulf, across Pakistan, to western China.

* According to a Pew Global Attitudes Project (http://pewglobal.org)

survey of Pakistani public opinion in 2010, 85 percent of respondents said they had a favorable view of China, and 3 percent said they had an unfavorable view.

* Pakistani President Asif Ali Zardari has visited China frequently, and urged China to invest more in his country.

TRADE HOPES

* Annual two-way trade was worth $8.7 billion in 2010, a rise of 27.7 percent on the previous year, according to Chinese statistics.

* Trade flows go heavily in China's favor, and last year it exported goods worth $6.9 billion to Pakistan, a rise of 25.5 percent on 2009, while Chinese imports from Pakistan were worth $1.7 billion, a rise of 37.2 percent.

* Pakistani officials have recently said the neighbors could increase bilateral trade to $15 billion a year by the end of 2012.

* China helped build Gwadar port in Baluchistan, and the Karakoram Highway, connecting northern Pakistan to far western China, which could be upgraded to provide a conduit for Chinese energy imports from other markets.

SECURITY CONCERNS

* China has urged mainly Muslim Pakistan to take action against Uighur militants from the western Chinese region of Xinjiang who have slipped in to Pakistan in past years.

* On July 5, 2009, violence broke out between Muslim Uighurs and Han Chinese in Xinjiang, killing 197 people, many of them Han residents attacked by Uighurs. Pakistan deplored the riots, winning praise from China for its stance.

* During a visit to Xinjiang in August, President Zardari promised to work closely with China in the fight against terrorism, after Chinese officials blamed militants trained in Pakistan for an attack in the region.

* The safety of Chinese nationals working in Pakistan has also been a major concern for China. Several Chinese workers were killed in militant attacks in Pakistan in recent years.