* FTSE 100 up 0.2%, FTSE 250 up 0.1%
* AB Foods gains after annual results
* Oil cos biggest gainers on main board
* Gambling firms fall for 2nd straight day (Adds company news items, analyst comment, chart, updates share moves)
Nov 5 (Reuters) - Gains for oil company shares pushed London's FTSE 100 into the black on Tuesday, helped by a prediction that OPEC would supply a shrinking portion of global supply, while Primark owner Associated British Foods jumped 5% after strong results.
The FTSE 100 gained 0.2% by 0810 GMT, hovering close to a one-month high it touched in the previous session, while the mid-cap index was 0.1% higher.
Oil majors Shell and BP, which fell last week after reporting falls in profit, were the biggest boost to the main index, opening higher and extending gains after OPEC said it expected to supply a diminishing amount of oil in the next five years in the face of competition from U.S. shale and other rival sources.
A.B.Foods headed for its best day in more than 10 months after it posted higher annual earnings and said it was well-positioned for further earnings growth in the new year.
Hopes that Washington and Beijing were on course to sign some form of trade deal continued to help the index.
Miners, one of the sectors most exposed to the tensions due to their dependence on Chinese demand, reached a near 2-month high, also helped by a rise in copper prices driven by a cut in forecasts by Chilean-focussed Antofagasta.
A mixed set of results pushed tobacco company Imperial Brands marginally higher after a volatile morning.
While sales for the year topped market expectations, the tobacco firm guided to low-single digit revenue and profit growth for the year amid a regulatory crackdown on vaping in the United States.
Among mid-caps, gambling and related firms fell for a second straight day after lawmakers called for a raft of measures to overhaul online casinos. William Hill, Rank Group and Playtech lost between 2.5%-4.4%.
(Reporting by Muvija M and Shashwat Awasthi in Bengaluru; Editing by Saumyadeb Chakrabarty and Patrick Graham)