The federal government is set to name a career diplomat as Canada's next ambassador to China after strongly considering making the appointment a political one as part of Canada's push to deepen ties with Beijing.

Guy Saint-Jacques, currently Canada's chief negotiator and ambassador for climate change, will take over as Canada's top representative in mainland China from Ambassador David Mulroney, according to people familiar with the matter.

The appointment of Mr. Saint-Jacques to what is now considered Canada's second-most important diplomatic posting behind the ambassador to the United States, comes at a critical juncture in relations with China and after Ottawa tried to go a different route. According to sources, the government hoped to name a senior political appointee c lose to Prime Minister Stephen Harper to the post, which would have signalled to Beijing that Canada desired more direct relations between leaders of the two countries.

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A senior political appointee would be received in China by officials close to the political leadership, opening access to China's top leaders and making for closer high-level relations.

Two former cabinet ministers – David Emerson, the former foreign affairs minister, and former trade minister Stockwell Day – were approached about the post, sources said. Neither wanted it.

While Mr. St. Jacques, as a veteran diplomat, will get normal access from the Ministry of Foreign Affairs, a political appointee would be more likely also to meet with senior Communist Party members. China's nominal foreign minister, for instance, is Yang Jiechi. However, Dai Bingguo, who heads the foreign affairs task force of the Central Committee of the Communist Party, is more powerful in setting foreign policy.

Mr. Saint-Jacques is a Mandarin speaker and China hand who is expected to be well received by the Chinese. But some observers were disappointed Ottawa couldn't find a candidate with more clout who would reflect China's growing importance to Canada.

"I was hoping for an upgrade to a stronger figure," said Charles Burton, a China expert at Brock University and a former diplomat at the Canadian embassy in Beijing. "Guy Saint-Jacques is a non-partisan, professional and highly competent public servant, but it's not the direction I was hoping [the posting] would take. It doesn't indicate the post is taking on a higher profile in Ottawa."

Canada's second-largest trading partner, China is key to the Conservative government's increasing focus on international trade. Initially cold to Beijing when elected in 2006, Mr. Harper and cabinet members have begun making frequent visits to China, which now has the world's second biggest economy. Canadian exports to China reached $17-billion (U.S.) in 2011, up from $2.7-billion in 2001. Last year, Canada imported $48.6-billion worth of Chinese goods, compared to $8.2-billion a decade before.

Mr. Saint-Jacques, one of the few high-ranking Canadian diplomats who speaks Mandarin, was at the top of the list of career diplomats up for the post, according to sources. He is a former number two in both the Washington and London embassies and once served as head of the political section in Canada's embassy in Beijing.

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Mr. Saint-Jacques's name has been submitted to the Chinese government, and approval is expected to be swift. Sources say he could formally assume the post as early as the end of October.

That may too late for the coming transfer of power in Beijing. Seven of the current nine members of the supreme Standing Committee of the Politburo are expected to retire this fall, moving aside for a new generation headed by Vice-President Xi Jinping. The new shape of China's leadership will be known only after a national meeting of the Communist Party leadership between September and November.

While he may not be a high-profile politician, Mr. Saint-Jacques's posting as chief negotiator at international climate change talks – a file on which he regularly butted heads with Chinese negotiators who wanted the developed world to bear the responsibility for combatting global warming – shows "he does enjoy the confidence of the Prime Minister," Prof. Burton said.

The challenge will be building on the momentum that the China-Canada relationship has gained over the past few years, progress widely attributed to Mr. Mulroney. When Mr. Mulroney was appointed in 2009, the relationship between Beijing and Ottawa was in something of a deep freeze, and ties have warmed dramatically in the past three years, culminating in Mr. Harper's tour earlier this year, in which he accepted a pair of pandas (on expensive 10-year loans) as a symbol of deepening friendship between the two countries.

However, greater challenges lie ahead, particularly on trade, where China has been demanding ever greater access to the Canadian market while refusing full reciprocity in how it treats Canadian firms. At the same time, Mr. Harper has been accused of ignoring the human-rights file, which he once proclaimed was dear to his heart.

A spokesman for the Prime Minister's Office, Carl Vallée, declined to confirm the appointment or comment.