The world increasingly believes China will become the top superpower but the United States enjoys a better image in most regions, according to a poll released Thursday.

A 39-nation study by the Pew Research Center found that the United States is still enjoying the boost to its reputation that followed the election of President Barack Obama -- except in a number of Islamic nations where Washington remains widely disliked.

The survey, the US-based center's largest since 2007, found growing criticism of China in most of East Asia and Europe.

"However, even in many countries where America is still seen as the top economic power, most believe China will someday become the leading overall superpower," the study said.

In Western Europe, the public in all countries polled except Italy -- where the United States was especially popular -- believed that China has topped or has already surpassed the United States "as the world's leading superpower."

But the study put the US favorability rating globally a 63 percent, compared with 50 percent for China. Even nations with widespread anti-US feeling gave higher marks when asked about the American people and most acknowledged that Washington allowed personal freedoms for its own citizens.

Relative perceptions of the United States and China varied widely among countries.

The biggest swing in the US favor was in Japan, where a territorial row with China has flared. A mere five percent of Japanese viewed China favorably -- far lower than in any other country polled -- while 69 percent were positive about the United States.

In the other direction, only 11 percent of Pakistanis saw the United States favorably against 81 percent who held positive views of China, which Islamabad often considers its key supporter.

Asia-Pacific nations were mostly supportive of the United States but divided on predicting the future. Two-thirds of Australians believed that China would emerge as the top superpower, a view shared by fewer than one-third in Japan, Malaysia and the Philippines.

Most economists believe it is only a matter of years before China, whose population is more than four times that of the United States, surpasses the United States in the raw size of its economy.

But many experts doubt that China will quickly catch up with the United States in the global reach of its culture, diplomacy and economy.

The Pew study found limited interest in Latin America and Africa in China's music and movies, although most admired the Asian power's technological advances.

China's image declined significantly over the past two years in Europe, dropping 11 points in Britain and nine percent in France.

The trend is likely due to "unease about China as a commercial competitor" as well as "European frustration with Chinese unilateralism in foreign affairs," the survey said.

Greece was the only European Union member where a majority held positive views of China and fewer than half of people were favorable toward the United States.

China's image also declined in several places where the United States is unpopular. In Egypt, China's favorability rating dropped 12 points to 45 percent, although it was still well above the 16 percent for the United States.

Outside the Islamic world, the United States was ranked worst in China, where 40 percent were favorable toward the United States, and Argentina, where the figure was 41 percent -- in contrast to a positive image of the United States in much of Latin America.

While Obama remained far more popular than his predecessor George W. Bush, the survey found widespread opposition to his pursuit of attacks with unmanned drones against alleged extremists in Pakistan and elsewhere.

Majorities only in the United States itself and in Israel and Kenya, countries with wide pro-US sentiment, supported the drone policy.

The Pew Research Center conducted the survey in March and April, before revelations of US electronic surveillance caused anger in Europe and before the military coup in Egypt.