$16.9 billion with China was labelled "crude oil". Because the National Iranian Tanker Company cannot defend the product on the oceans, it most often leaves port under the flag of another nation which is able to defend its own interests. The case of a Shanghai-based operator of oil tankers, Kunlun Holdings is illustrative: in early June it was operating with a shipment of Iranian crude oil as the Pacific Bravo before its transponder disappeared on 5 June in the Straits of Malacca. When it reappeared on 18 July, the ship had been relieved of its load and had been renamed to become the Latin Venture. The US, which had warned ports not to offload the $120 million cargo of the Pacific Bravo, was unhappy about the failure of its sanctions regime. Kunlun Holdings is owned by the Bank of Kunlun, which is in turn owned by the (SOE) CNPC. The Bank "has long been the financial institution at heart of China-Iran bilateral trade". Chinese foreign ministry spokesperson Geng Shuang "resolutely opposes" American unilateral sanctions. Oil production and reserves Total oil production reached a peak level of in 1976. By 1978, Iran had become the second-largest OPEC producer and exporter of crude oil and the fourth-largest producer in the world. After a lengthy decline in the 1980s, production of crude oil began to increase steadily in 1987. In 2008 Iran produced per day (bpd) and exported . Accounting for 5 percent of world production, it returned to its previous position as OPEC's second-largest producer. According to estimates, in 2005 Iran had the capacity to produce ; it was believed that production capacity could increase to to , but only with a substantial increase in foreign investment. Iran's long-term sustainable oil production rate is estimated at . According to the Iranian government, Iran has enough reserves to produce oil for the next 100 years while oil reserves of other Middle Eastern countries will be depleted in the next 60 years and most other oil-rich countries will lose their reserves within the next 30 years. In 2006 Iran reported crude oil reserves of , accounting for about 15 percent of OPEC's proven reserves and 11.4 percent of world proven reserves. While the estimate of world crude oil reserves remained nearly steady between 2001 and 2006, at , the estimate of Iran's oil reserves was revised upward by 32 percent when a new field