* U.S. drilling activity continues to rise
* OPEC's supply cuts undermined by higher U.S. output
* Brent prices heading for near 20 percent fall in H1 (Updates with comment, refreshes prices)
LONDON, June 26 (Reuters) - Oil prices steadied above last week's seven-month lows on Monday, hemmed in by a relentless rise in U.S. supply, bloated global inventories and a surge in demand for short sale contracts that signal investors see potential for a price fall.
Investors in U.S. crude futures and options increased their bets against a further rise in prices, as the number of U.S. oil rigs in operation hit its highest in over three years.
U.S. shale oil output is up around 10 percent since last year, while places like Brazil have also hiked output.
The rise in supplies threatens to scupper efforts by the Organization of the Petroleum Exporting Countries and its partners to reduce global oil inventories with production cuts.
Brent crude futures were flat at $45.54 a barrel by 1335 GMT, set for a near 20 percent drop in the first half of the year. It hit a trough of $44.35 on June 21, its lowest level since November.
U.S. West Texas Intermediate crude futures were up by just 3 cents at $43.04 a barrel.
"We saw this continued big rise in oil rigs last week and in our view we dont need a single additional rig for the next 12 months in the U.S. space if we look at balance for 2018," SEB strategist Bjarne Schieldrop said.
"I dont think OPEC is going to cut deeper, at least not for now. I think its keeping its fingers crossed and looking forward to Q3 and Q4 and hoping their medicine will do the trick," he added.
OPEC states and 11 other exporters agreed in May to extend cuts of 1.8 million barrels per day (bpd) until March 2018, in the hope that it would force global supply and demand to align.
Traders and analysts said there was little fundamental news to justify much of a bounce in oil prices.
"I'm seeing little to convince me that this is anything other than a dead cat bounce," OANDA senior market analyst Craig Erlam said.
"A break above $44.50 in WTI and $47 in Brent may suggest were seeing a broader correction, something that at this stage is looking unlikely," he said.
Analysts at Bank of America-Merrill Lynch said demand had not grown quickly enough to mop up any excess output.
"Looking into the second half of 2017, we now doubt that demand growth will accelerate sufficiently," they wrote. (Additional reporting by Jane Chung in Seoul; Editing by Dale Hudson and Edmund Blair)