(Reuters) - The United States may not yet be in love with football, but more Americans became fans as the World Cup in Brazil progressed, according to an ongoing Reuters/Ipsos poll.

Fifty-six percent of Americans said they were following the World Cup as it headed into the semi-finals, compared with 39 percent polled during the first week of the tournament.

Strong performances by the U.S. team, which made it to the second round before being knocked out by Belgium, helped galvanize spectator interest in a sport whose worldwide popularity has generally not extended to the United States.

The World Cup "has been fun to watch," said Josh Morris, 28, of Gladwin, Michigan.

"Four years ago, I hardly knew the last World Cup existed," said Morris, who usually follows Major League Baseball and the National Football League on a weekly basis. "I still wouldn't call it my favorite sport, but my interest is tenfold what it was."

And while football may not have reached the national-obsession level it has in South America and Europe, the U.S. team's group game against Portugal was the sport's most-watched in U.S. history. An estimated 24.7 million tuned in on ESPN and Spanish-language broadcast network Univision.

Americans have also become more clued in about the tournament with each game, the poll shows. About 62 percent had heard or read about the World Cup by this week, compared with only half of respondents three weeks ago.

As for Americans' predictions of who will win the tournament? Polled on the eve of the semi-finals, double the number of respondents backed Germany over Argentina. The two teams will compete for the trophy on Sunday.

Six percent of Americans polled still said their home team had a chance of winning - even though the United States was no longer in the tournament.

The Reuters/Ipsos online polls were of 1,365 adult Americans June 13-17 and 1,674 July 4-8. The credibility interval, a measure of precision, is plus or minus 3.2 percentage points for the poll in June and plus or minus 2.7 percentage points for the one in July.