White sugar futures on ICE rallied on Tuesday on fears over tight supplies before a contract expiry later this month, while robusta coffee steadied near a one-year high, underpinned by strong physical demand. London coocoa was supported by a weaker pound in the fallout of Britain's vote to leave the EU. White sugar futures jumped on concerns over tight supplies before the August contract expiry on July 15. "The trade shorts are on the run as they finally wake up to the fact there won't be any significant deliverable supplies against the August expiry," a senior trade source said. "Watch the August fly!" August white sugar was up $14.30, or 2.5 percent, at $579.20 per tonne at 1121 GMT, after surging to a contract high at $581.20. October raw sugar futures were up 0.13 cent, or 0.6 percent, at 20.91 cents a lb. On Thursday the most-active contract hit a more than 3-1/2-year high of 21.22 cents a lb, buoyed by a shift of the global market into deficit after years of surpluses. Robusta coffee futures held steady near a one-year high, supported by strong physical demand. Dealers said there was a wide arbitrage between arabica and robusta futures prices, boosting the appeal of robusta buying. They noted a premium of 65-66 cents a lb of September arabica futures over September robusta, compared with a premium of 48 cents a lb in mid-June. "That creates tremendous encouragement to buy robustas," a senior coffee trader said. Arabica futures dipped, but were underpinned by concerns over the quality of beans in Brazil's current harvest after heavy rainfall. ICE September arabica futures were down 0.6 cent, or 0.4 percent, to $1.4580 per lb. September robusta coffee was down $2, or 0.1 percent, at $1,766 per tonne, having touched a one-year high of $1,773 on Monday. London cocoa futures edged up, supported by the weak pound, which hit a fresh 31-year low against the dollar, as investors worried about the economic and financial implications of Brexit. London September cocoa was up 26 pounds, or 1.1 percent, at 2,412 pounds per tonne, after touching a contract high of 2,414 pounds. September New York cocoa was up $23, or 0.8 percent, at $3,018 per tonne.