It was not so much a happy ending ... as a noisy one.

When Tim and Beth Alberts stepped out of a church in downtown Chicago on Saturday, they found their wedding had been crashed - by thousands of anti-war protesters.

The newlyweds had wanted to take wedding pictures with the city's financial district as a backdrop, but were instead surrounded by marchers demanding an end to costly and destructive wars as the leaders of more than 50 nations, including Australian Prime Minister Julia Gillard, discussed the withdrawal from Afghanistan at a NATO summit.

"Let's get out of here," Mrs Alberts said brusquely after she shared a hug and kiss on the street with her husband, the Chicago Sun-Times reported.