Advice prepared by department officials for the next minister of foreign affairs says Canada has a "strong national interest in sustaining" the United Nations as a "means of achieving our foreign policy priorities."

The document obtained by CBC News, marked "secret" and dated this month, offers an assessment of the challenges facing the UN, including whether the multilateral organization can cope with the demands placed upon it.

And it warns a "diminished UN would constrain Canada's ability to advance its priorities."

The Conservative government has at times expressed disdain for the UN, although it remains one of the organization's top 10 financial contributors.

As prime minister, Stephen Harper has chosen at times to skip the annual opening session even while he was in New York, although he addressed it last year as well as in 2010 and 2006. (This is not far out of line with previous prime ministers; Brian Mulroney addressed the General Assembly three out of eight years, Jean Chrétien five out of 10.)

In 2012, then foreign affairs minister John Baird criticized the UN at the General Assembly for spending too much time on itself.

At that time, the Conservatives also decided not to bid again on a Security Council seat after losing in 2010.

The foreign affairs document suggests Canada declare its candidacy for a potential seat on the council as soon as possible, which it notes is realistically not until 2023-24. The document says this would signal a "renewed commitment to the international security agenda."

The memo says this would also allow Canada to shape the effectiveness of the UN in the years ahead.

The document suggests that could be done by leveraging Canada's large financial contribution to encourage better accountability and by targeting some key areas, including increased personnel for UN peacekeeping, more work on disarmament and humanitarian issues and even an attempt to place more Canadians in senior positions within the organization.

'Consider adjusting ... tone'

The document, titled "Analysis and recommendations: Canadian engagement with the United Nations," was prepared by department officials to advise the minister who will assume the foreign affairs portfolio after the Oct. 19 election.

Part of that advice is a recommendation that the government consider "adjusting Canada's overall tone and approach" in order to be an effective player at the UN and to influence issues on the international stage.

The document highlights the many things Canada has working in its favour with a "credible reputation and extensive expertise and knowledge."

While the document does not dictate what Canada should do, it clearly promotes the idea that engagement with the UN is the better foreign policy option.

But it also includes some warnings of what that decision might mean.

It says it will require Canada to be willing to engage with a "range of international actors, including non-like-minded."