* C$ touches high of C$1.0003 vs US$ or 99.97 U.S. cents * Bond prices climb across the curve * Canadian GDP due at 8:30 a.m. By Claire Sibonney TORONTO, July 31 (Reuters) - Canada's dollar nearly cracked parity against its U.S. counterpart on Tuesday, but then pulled back from an 11-week high as investors feared a recent rally built on hopes of new stimulus from central banks in the United States and Europe had been overdone. Riskier assets have been boosted by mounting expectation that the European Central Bank will revive its bond buying program to help lower the borrowing costs of debt-stricken Spain and Italy, while the U.S. Federal Reserve has been under renewed pressure to support flagging growth. Both central banks hold policy meetings this week. Last week, ECB President Mario Draghi said the ECB was ready to do whatever it takes to preserve the euro. "Draghi especially ... has put his personal credibility on the line which is something that's extraordinarily rare in central banking," said Adam Button, currency analyst at ForexLive in Montreal. "The market is now alight with speculation about some of the fantastic things they might do and that goes for the Fed as well, to some lesser extent, so right now we're going to witness the full power of central banking." At 8:08 a.m. (1208 GMT), the Canadian dollar stood at C$1.0023 versus the greenback, or 99.77 U.S. cents, slightly softer than Monday's North American session close at C$1.0018 against the greenback, or 99.82 U.S. cents. Earlier the Canadian currency touched C$1.0003, or 99.97 U.S. cents, its firmest level since mid-May. Domestic growth data for May is due at 8:30 a.m. (1230 GMT)) and is expected to provide further direction. "If we get a very strong (GDP) report the Canadian dollar can bust right through parity," added Button, noting some resistance for the domestic currency around C$0.9955. Canadian bond prices climbed across the curve with the two-year bond up 2 Canadian cents to yield 1.080 percent, and the benchmark 10-year bond up 19 Canadian cents to yield 1.680 percent.