UK stocks snapped a five-day winning streak on Thursday morning as hopes for an overnight Greek debt deal were dashed, with Athens and its creditors failing to come to an agreement.The FTSE 100 was trading 0.21% lower at 6,830.50 early on.Greece remained "firm on its position", according to a Greek government official, as the Hellenic nation rejected calls on Wednesday night to accept more austerity measures in exchange for unlocking further aid.Hans-Jörg Schelling, the Austrian finance minister, criticised Greece's attitude towards debt restructuring as "the most significant chunk" in the negotiations, while German counterpart Wolfgang Schäuble said there were still large differences on pension changes.The country faces a €1.6bn repayment to the IMF on 30 June and must reach a deal with its creditors before that date to unlock further aid or default on its debt."Talks have resumed at the technical level this morning and PM Tspiras will meet the heads of the three institutions this morning in an attempt to close remaining differences which remain between the country and its creditors," explained analyst Philippe Gudin from Barclays.However, Gudin said he still expects a partial agreement to avoid a default next week and extend the programme beyond the end of the month.A raft of economic data from the States will also be in focus on Thursday afternoon: analysts predict a 6,000 rise in jobless claims, 0.5% and 0.7% increases in personal income and spending respectively, and a small rise in the Markit US services PMI.Admiral dropsInsurer Admiral was trading sharply lower after Citigroup downgraded the stock to 'sell' from 'neutral', saying it's a high-quality name, but fully valued. The bank said it sees limited room for price-to-earnings expansion, given the growth profile is unlikely to return to historical levels, even assuming an upswing in UK motor rates.Blue chips Compass, Experian and United Utilities were also lower after going ex-dividend.Supermarket giant Tesco advanced on rumours that private equity firms Affinity Equity Partners, Carlyle Group and CVC Capital Partners were among seven or eight preliminary bidders for Tesco's South Korean unit.Mining stocks were mostly in the red, with heavyweights BHP Billiton and Glencore among the worst performers.Recycled packing maker DS Smith gained after posting a 20% rise in full-year pre-tax profit and a 14% increase in the full-year dividend.Department store Debenhams also advanced after saying it was on track to meet full-year gross profit targets, helped by a 0.9% improvement in like-for-like sales.Market MoverstechMARK 3,192.93 -0.16%FTSE 100 6,830.50 -0.21%FTSE 250 17,915.74 -0.05%FTSE 100 - RisersSage Group (SGE) 521.50p +1.07%ARM Holdings (ARM) 1,136.00p +0.98%Barratt Developments (BDEV) 623.50p +0.89%Mondi (MNDI) 1,428.00p +0.78%Sports Direct International (SPD) 730.50p +0.55%Capita (CPI) 1,267.00p +0.48%Tesco (TSCO) 216.80p +0.46%BP (BP.) 444.00p +0.43%Vodafone Group (VOD) 240.75p +0.42%Royal Dutch Shell 'B' (RDSB) 1,923.50p +0.37%FTSE 100 - FallersUnited Utilities Group (UU.) 953.50p -3.83%Admiral Group (ADM) 1,396.00p -2.45%Experian (EXPN) 1,195.00p -1.24%Compass Group (CPG) 1,100.00p -1.17%Centrica (CNA) 276.80p -1.07%Shire Plc (SHP) 5,345.00p -1.02%AstraZeneca (AZN) 4,207.50p -1.00%Schroders (SDR) 3,300.00p -0.90%Glencore (GLEN) 275.90p -0.76%Severn Trent (SVT) 2,177.00p -0.73%FTSE 250 - RisersPetrofac Ltd. (PFC) 973.50p +3.84%Smith (DS) (SMDS) 385.00p +2.39%Redrow (RDW) 450.70p +1.49%Carillion (CLLN) 356.10p +1.31%Capital & Counties Properties (CAPC) 428.20p +1.28%Crest Nicholson Holdings (CRST) 563.50p +1.26%Foreign and Colonial Inv Trust (FRCL) 449.70p +1.22%Just Retirement Group (JRG) 179.10p +1.19%Bovis Homes Group (BVS) 1,130.00p +1.16%Debenhams (DEB) 91.35p +1.16%FTSE 250 - FallersElectrocomponents (ECM) 221.20p -3.66%PayPoint (PAY) 988.50p -3.09%Jimmy Choo (CHOO) 155.20p -3.00%Mitie Group (MTO) 317.20p -2.64%Greencore Group (GNC) 306.10p -1.99%Fidelity China Special Situations (FCSS) 161.50p -1.76%Pennon Group (PNN) 840.50p -1.64%Wizz Air Holdings (WIZZ) 1,564.00p -1.64%Diploma (DPLM) 794.50p -1.61%JD Sports Fashion (JD.) 692.00p -1.56%