Markets are expected to open with losses on Tuesday morning as traders return to their desks after the long three-day weekend, attempting to play catch-up after negative sessions in the US and Asia overnight. City sources predict the FTSE 100 will open down around 25 points from Friday's close of 6,492.10.Benchmarks on Wall Street finished lower last night as concerns over Syria and the US debt ceiling weighed on sentiment.US Secretary of State John Kerry said last night that Syria would be held accountable for the "moral obscenity" of the chemical weapons attack that has killed well over a thousand. "By any standard it is inexcusable," he said.Senior Market Analyst Michael Hewson from CMC Markets said that the comments "raised concerns that some form of confrontation could be being considered".   Meanwhile, Treasury Secretary Jacob Lew was reported saying that the US government would reach the debt ceiling by mid-October unless Congress agrees to raise the limit. "Operating the government with no borrowing authority, and with only the cash on hand on a given day, would place the US in an unacceptable position," Lew said. Stocks to watch Antofagasta's revenues in the first half dropped 12.1% to $2.7bn, reflecting a decline in copper prices and increased costs. Earnings before interest, tax, depreciation and amortisation fell 31.2% to $1.2bn following the average London Metal Exchange price of copper falling by 6.8% and realised copper prices sliding 15.5%.Oilfied services group Petrofac saw both revenues and profits slip in the first half but said that it remains on track to deliver growth for the full year. "As previously guided, our revenue and net profit for 2013 is expected to be significantly weighted towards the second half of the year, reflecting the phasing of project delivery," the company said.Bovis Homes has agreed a further banking arrangement, providing the group with additional financial flexibility. The £50m agreement extends the £125m committed revolving credit facility agreed in January 2013, and combined with the three-year term loan of £25m entered into in January 2013, the group now has £200m of facilities.