May 21 (Reuters) - Halliburton Co, the world's second-largest oilfield services company, said on Tuesday that Mexican state oil company Pemex was delaying any significant activity at its Burgos and Chicontepec projects until next year. Chief Financial Officer Mark McCollum said Halliburton's Latin American margins would be weighed down this year by the reduction in activity at the projects. He added that Pemex, ahead of a July tender on the projects, was also reducing rigs run by Schlumberger and Weatherford. "They're essentially delaying significant activity until 2014," McCollum said at the UBS Global Oil and Gas Conference. Shares of Halliburton fell 2.2 percent to $44.51 in early trading on Tuesday. In North America, McCollum said the market for pressure pumping equipment - used for hydraulic fracturing of wells - remained 20 percent over-supplied, which should be reduced by half by the end of 2013. There was further pricing pressure in North America in the second quarter, he added, though the number of rigs working in the region should rise by between 100 and 150 rigs by the end of 2013.