WASHINGTON (Reuters) - A plurality of Americans see relations with China as the most important globally for the United States, a survey published on Tuesday showed, but more than half of those polled viewed China was an adversary.

The Thomson Reuters/Ipsos poll of 1,077 adults aged 18 and older across the United States a fortnight before President Barack Obama's first official visit to China highlights U.S. ambivalence about the key trade and diplomatic partner.

Asked to choose from a list of countries "the most important bilateral relationship the United States should have," 34 percent chose China. Next was Britain, selected by 23 percent; and Canada, the choice of 18 percent.

When asked to characterize China as either an "ally" or an "adversary," 56 percent characterized China as a foe, while only 33 put the country in the ally column, said Ipsos Public Affairs, which conducted the poll for Thomson Reuters.

Two percent of Americans said China was both an ally and adversary, the same percentage who said it was neither. Seven percent responded "don't know," the nonpartisan polling firm said.

The poll, conducted between Oct. 29 and Nov. 2, had a margin of error of 3.1 percentage points, Ipsos said.

Obama makes a key visit to China and other Asian countries next week at a time when Washington and Beijing are working closely on tackling the global financial crisis, climate change and how to handle diplomatic hot spots like North Korea.

But the two countries have skirmished over trade issues. U.S. manufacturing and labor groups frequently accuse the Chinese of mercantilist business practices that have put American firms out of business with a loss of millions of jobs.

(Reporting by Paul Eckert; editing by Todd Eastham)

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