The Royal/Dutch Shell group of companies has defended its decision to help build the 4,000km west-east gas pipeline opposed by human-rights groups.
Philip Watts, chairman of the group's committee of managing directors, said Shell would ensure the pipeline was designed according to best international practice.
British Petroleum (BP) dropped out of the project in the face of a vocal opposition from the pro-Tibet lobby and environmentalists.
PetroChina has struggled to find foreign partners for the huge project that forms a core element in Beijing's west-development programme; its length means it is not considered commercially viable in the medium term.
Human rights groups are also targeting BP and Morgan Stanley, which are indirectly involved in another PetroChina pipeline to bring gas from the Qaidam basin in Qinghai about 950km to Lanzhou. BP has a US$578 million investment in PetroChina.
In an interview in Beijing, Mr Watts answered repeated questions about the political risks of taking part in developing gas fields in the Tarim basin in Xinjiang, where China is suppressing unrest among the indigenous Uighur population.
