Sharecast - At 0900 BST, the FTSE 100 was down 0.2% at 7,750.93.
US consumer price inflation data for April is due at 1330 BST.
Susannah Streeter, head of money and markets at Hargreaves Lansdown (LON:HRGV), said: "The extent to which price pressures are still weighing on the American economy is in sharp focus today, with investors watching and waiting for the latest inflation snapshot. This is a big piece of the puzzle for central bank policymakers and will help them decide on whether to press pause on rate hikes in June.
"If headline CPI comes in, as expected, around 5% and core prices, stripping out volatile food and energy, drop slightly back, it will indicate that monetary policy has been wound tight enough to keep prices cranking down. There will still be worries that due to the lag effect, aggressive rate hikes might still bring stronger than expected disinflationary shockwaves in the months to come, which could push the US into a deeper downturn. This is being reflected in oil prices with Brent Crude dropping back below $77 a barrel, as traders assess the potential knock-on effects of a US recession on global demand."
In equity markets, Asos slumped as the fast fashion retailer reported a widening of its interim losses as shoppers continued to tighten their belts amid the cost-of-living crisis, but the company said it was confident of a return to profit in the second half.
Holiday giant Tui fell despite reporting narrower losses and an increase in revenue as travel rebounded from the Covid pandemic. Second-quarter underlying losses before interest and tax came in at €242.4m, compared with a €330m loss a year ago.
On the upside, Melrose Industries (LON:MRON) surged after saying it was trading "materially ahead" of expectations, with significant growth in revenue, profit and margin being achieved, as it issued new guidance for the full year.
Caterer Compass Group (LON:CPG) gained after it lifted its full-year guidance as it posted a jump in first-half revenue and operating profit.
Pub chain Wetherspoons was also up after saying it expects annual earnings to be at the top end of expectations and tipped 2023 to be a record year for sales.
Harbour Energy (LON:HBR) pushed higher as it held full-year guidance after a reporting a strong first quarter.