LONDON (AFP) - World oil prices sank on Monday, extending heavy pre-weekend losses as weak global stock markets and the US-China trade row dented investor sentiment. New Yorks main contract, light sweet crude for October delivery slid 48 cents to 68.81 dollars per barrel. Brent North Sea crude for October delivery dipped 19 cents to 67.50 dollars in early afternoon London trade. The fall is really related to some weakness in equities markets, said Victor Shum, senior principal at energy consultancy Purvin and Gertz in Singapore. Japanese share prices tumbled 2.32 percent on Monday as investors fretted about pre-weekend losses on Wall Street and a stronger yen, leading to a fall in Asian equities. Europes main stock markets also fell on Monday, at one stage losing more than one percent in Frankfurt, London and Paris. We continue to have this tug-of-war between weak supply fundamentals and optimistic hopes of economic recovery, so we are likely to stay in this 65 dollar to 75 dollar range, Shum added. Oil had slumped Friday as traders banked profits from a four-day rally spurred by growing optimism that the global economy was emerging from recession. Before the weekend, New York crude dived 2.62 dollars on Friday and London Brent oil wiped out 2.17 dollars after fresh falls on Wall Street. Crude futures fell nearly four percent on Friday as US equities slid, causing a moderation of expectations for the strength of global economic growth and recovery in oil demand, said Sucden analyst Nimit Khamar. He added that the worsening China-US trade dispute was also dampening the market. The United States is the worlds biggest energy consuming nation followed by number two China. The trade row between China and the US is also weighing on market sentiment, as increased protectionism could hinder a global economic recovery, Khamar said. US President Obama on Friday announced additional duties on Chinese manufactured tires. In response Beijing accused Washington of 'rampant protectionism and threatened action against US auto and US poultry imports. China on Monday hauled the United States to the World Trade Organisation over what it alleged were unfair tariffs imposed by Washington on Chinese tyre imports. The White House on Friday imposed punitive duties of an extra 35 percent on Chinese-made tyres amid warnings that a surge in the Chinese-made goods had cost more than 5,000 jobs in the United States. Last week, meanwhile, the Organization of the Petroleum Exporting Countries decided to maintain its production levels as the cartel deemed the market to be oversupplied. OPEC pumps about 40 percent of world oil supplies.