SHOCKED: United States cycle tourists Russ Roca and Laura Crawford. "The whole thing was surreal,'' said Mr Roca.

A road rage attack on an American cyclist in Wellington has been condemned as an embarrassment to New Zealand.

Russ Roca, 33, was tackled to the ground and punched in the face by a motorist in Newtown on Tuesday.

Roca and his partner, Laura Crawford, 32, of Oregon, have been riding the New Zealand Cycle Trail for more than a month without any problems from motorists.

They were riding their collapsible bikes on a two-lane section of Riddiford St about 4.30pm when a man driving a silver sedan passed them "really really close, almost aggressively", he said.

"So the natural reaction was to shout 'What's going on?' We threw our hands up, and there was a finger gesture."

The motorist, described as a 30-something male of average build with black hair, pulled over and came at the cyclists, Roca said.

"Laura swerved around him but I wasn't so lucky. He ran after me, tackled me and pushed me off my bike.

"When I got up, he wasn't finished and he punched me in the face."

The attack was over as quickly as it began, with the man returning to his car and speeding off, running a red light in the process, Roca said.

He was left with sore shoulders and legs and a cut on the inside of his mouth, but said the emotional shock was the worst injury he sustained.

Crawford said the man had shouted in a foreign language as he approached.

The incident was witnessed by passers-by and other motorists who took down the car's licence plate number, she said. The incident has been reported to police.

The couple have been writing a cycling travel blog www.pathlesspedaled.com since 2009, and Roca said they had been warned before they came to New Zealand of the country's "crazy drivers".

Last year German cyclist Mia Susanne Pusch, 19, blogged about the perils of cycling on New Zealand roads, describing Kiwi truck drivers as "beasts". She died after colliding with a truck and trailer near Bulls.

Roca said his experience had not put the pair off cycling in New Zealand, but made them revise their view of the country. "The whole thing was surreal."

Cycling Advocates Network spokesman Patrick Morgan said the attack was embarrassing to New Zealand. "This assault is unacceptable but unfortunately ... not rare."

Driving culture in New Zealand needed to change to make motorists more tolerant of cyclists, Roca said.