OTTAWA — Ever since President Obama said in June that a litmus test for the proposed Keystone XL oil pipeline from Canada was whether it would “significantly” worsen global warming, Canadian government officials have insisted it would not.

They reasoned that because the pipeline would not have any major effect on rate of development of Canada’s oil sands, as a State Department environmental review concluded in March, it would not significantly raise the amount of carbon emitted.

But documents obtained by a Canadian environmental group suggest that the staff at Natural Resources Canada viewed Keystone XL as an important tool for expanding oil sands production. The documents were released to the Pembina Institute, a group based in Calgary, Alberta, after a request made under Canada’s Access to Information Act.

Briefing notes prepared for the natural resources minister, Joe Oliver, before a trip to Chicago to promote Keystone XL in March, noted that “in order for crude oil production to grow, the North American pipeline network must be expanded through initiatives, such as the Keystone XL Pipeline project.”