(Adds economist quotes and details throughout; updates prices) * Canadian dollar falls 0.2% against the greenback * Loonie notches fourth straight weekly gain * Price of U.S. oil settles 0.5% lower * Canadian bond yields ease across the curve By Fergal Smith TORONTO, Dec 11 (Reuters) - The Canadian dollar weakened against its U.S. counterpart on Friday as investors worried about the risk of a disorderly Brexit and delays over a U.S. fiscal package, with the currency pulling back from a two-and-a-half-year high the day before. The loonie was trading 0.2% lower at 1.2763 to the greenback, or 78.35 U.S. cents, after touching on Thursday its strongest intraday level since April 2018 at 1.2702. For the week, the currency was up 0.1%, its fourth straight weekly advance. "After many weeks marked by optimism , it would be normal to see a period of consolidation," said Hendrix Vachon, a senior economist at Desjardins. "The bad news about Brexit negotiations and the lack of a new stimulus package in the U.S. are fuelling pessimism." Global equity markets fell after British Prime Minister Boris Johnson said Britain is likely to complete its journey out of the European Union in three weeks without a trade deal and U.S. House of Representatives Speaker Nancy Pelosi raised the possibility of stimulus negotiations dragging on through Christmas. Canada sends about 75% of its exports to the United States, including oil. U.S. crude oil futures settled 0.5% lower at $46.57 a barrel as demand worries due to new coronavirus-related restrictions on business in New York overshadowed progress toward vaccination programs. In Canada, federal health authorities said that longer-range forecasts project the second wave of the coronavirus spreading rapidly through Canada and all the major provinces need to impose more restrictions. "There are still many uncertainties for the very short term," Vachon said, adding that the loonie is more likely to weaken to 1.30 than reach 1.25 during the winter. Canadian government bond yields were lower across the curve in sympathy with U.S. Treasuries. The 10-year fell 2.1 basis points to 0.714%. (Reporting by Fergal Smith; editing by Jonathan Oatisthe Organization of the Petroleum Exporting Countries (OPEC))