CNOOC never received explicit approval from the Beijing government for its daring $18.5bn bid for US energy group Unocal - a lack of support that contributed to this week's collapse of the Chinese group's takeover attempt.
The disclosure of the part played by Beijing in CNOOC's withdrawal, which enabled Chevron to win Unocal for about $17.6bn, will heighten investor concerns at the ability of Chinese companies to clinch large takeovers.
Despite protests from US politicians that the state-controlled group's bid was sponsored by Beijing, people close to the situation said the Chinese authorities steered clear of the Unocal takeover battle.
Diplomatic contact between Beijing and Washington might have helped CNOOC's offer weather political opposition on Capitol Hill or at least given the Chinese group confidence a takeover would not be blocked on national security grounds, according to people familiar with the matter.
But "the Chinese government was never behind it," said one.
As a Hong Kong-listed state company, CNOOC does not need Beijing's permission for an overseas takeover bid. But it is understood the company contacted top officials in state organisations before launching its $67 a share bid on June 23.
Observers believe Beijing might not have been wholly convinced of the merits of the bid.
Mr Fu's move has perplexed observers, giving rise to speculation Beijing might have asked him to withdraw.
Some leading academics have criticised CNOOC's bid, saying the target and the timing were wrong.
The Chinese government might also have wanted to prevent anything from overshadowing next month's Washington visit by China's president, Hu Jintao.
CNOOC's advisers, Goldman Sachs and JP Morgan, declined to comment.
A CNOOC spokesman said that as a Hong Kong-listed company, it typically would not need government approval for such a deal. It was only when the company needed to move money out of China that it would need approval from the State Administration of Foreign Exchange.