The move could direct a trade conflict between the world's two largest economies by months of relative calm in the markets and solid returns for investors.
Trump-risk trading negotiations scheduled for this week by warning Sunday that he could raise tariffs of $ 200 billion of Chinese goods to 25% from 10% on Friday .  China's Shanghai Composite cast 5.6%, while Shenzhen Composite, which includes many of the country's technical companies, shed 7.4%. Hang Seng fell 3% in Hong Kong.
European markets opened with losses. In export-driven Germany, DAX was down 1
Kit Juckes, a strategist at Societe Generale, said that business experts were uncertain about how to interpret Trump's threat.
"Does he try to put pressure on a deal this week? And if so, will it work, or will it remain?" Asked juckes. "It is in both American and Chinese interests to get an agreement made."
The revised offer increases the amount of cash included in the offer of $ 76 per share $ 59.
Vicki Hollub, CEO of Occidental, increased the pressure on Anadarko in a letter to the board dated Sunday.
"We remain confused about your apparent resistance to gaining far more value for Anadarko shareholders who have been clearly expressed through our interactions during the past week," she wrote.
The bidding war for Anadarko reflects an intense desire from US oil companies to acquire America's best shale shares. Occidental is already the oil producer No. 1 in the great Permian Basin.
On Monday, Occidental reported that net income in the first quarter was $ 631 million, down 11% from the last three months of 2018.