Brent crude futures for November settlement slipped $1.35, or 1.57 per cent, to $84.80 a barrel at 0640 GMT. US West Texas Intermediate (WTI) crude futures. declined to as low as $77.21, the lowest since Jan 6. The dollar index that measures the greenback against a basket of major currencies climbed to a 20-year high. A stronger greenback tends to curtail demand for dollar-denominated oil since buyers using other currencies must spend more to buy crude. Central banks in numerous oil-consuming countries, including the United States, have raised interest rates to fight surging inflation which has led to concerns the tightening could trigger an economic slowdown. Attention is turning to what the Organisation of the Petroleum Exporting Countries (Opec . . .