That's where American Sharon Heffley comes in. Heffley, who holds a masters degree in speech pathology, had been director of speech and language services for a county health department in Maryland. In 1987, she founded her company, the Accent Modification Centre, which helps people polish their speaking skills.

'This field probably developed with an influx of Asians to the US beginning in the 1970s,' she says. Indeed, according to government figures, more than 2.5 million Asian immigrants entered the US in 1980, a five-fold increase since 1960. In 1990, there were nearly 5 million. Heffley says that during the past two decades many well-educated professionals arriving in the US were unable to secure jobs they were technically qualified for due to poor communication skills.

'They often read and wrote English well when they arrived, but had little opportunity to speak the language,' she says. 'Or they spoke it with a very different English dialect.'

Today, 80 per cent of Heffley's clients hail from Asia, and probably half of those are Chinese, she says. Her clientele are a combination of private individuals and companies which send their staff.

Apart from Asians, Heffley says Latinos make up nearly 15 per cent of her clients, and she's begun to see larger numbers of Russians and Ukrainians. She has even worked with some tongue-tied Americans from Brooklyn, New York, the deep south and the midwest.

But with the opportunities being created by China's entry into the World Trade Organisation and its hosting of the 2008 Olympics, an increasing number of Chinese expatriates could ask for her expertise.

'No one at work said anything about my English,' notes Sih Lee, a Guangzhou-born computer executive who attends one of Heffley's classes. But when his technology firm offered to send him to the classes, he thought he had nothing to lose.

'Most of us are in the IT field,' says Taiwanese Geider Chen, who is in the same class. 'And a lot of time we are talking to each other, to other Chinese, in our native language. But the problem comes when we need to talk to our customers, who are all Americans.'

Their softly spoken instructor is highly selective in whom she accepts for her classes. 'I do not teach English, so they must have a good foundation in English and must be conversational,' Heffley says.

In fact, judging by today's trio of students, their English is excellent. Yet even at their level, American-accented English can be a veritable verbal minefield for non-native speakers. Apart from the confusing words, where cars are parked in 'driveways' but are driven on 'parkways', there are many bizarre spellings, and then there is the unfamiliar rhythm of speech.

'Visually, English words can often look one way, but actually sound another way,' Heffley says. 'Sometimes the same word will sound completely different when used for a different meaning. For example, we take a senior citizen to the blood mobile, but first ask them, are they mobile? And many English words have sounds you can't see on the written page, which are verbally stretched out longer than they appear on printed pages.'

Chinese immigrants are often proficient with English grammar rules, says Heffley, but they frequently fail to add the final consonant endings, such as t, d, s, and z that occur, and this can burden them with heavily accented English.

'Those who attended college here and interact socially with American-born students and those who've had children living here usually have the best skills,' she says.

Heffley uses a combination of verbal instructions, using detailed teaching materials which she developed and published herself, along with physiological techniques to guide her students to use the correct tone and pitch when speaking.

'The tongue has hundreds of muscles which are very flexible,' Heffley says. 'The lips and jaws are not nearly as flexible, so only using them slows the speaker down.'

Passing a hand mirror around, Heffley shows each student how words can come out differently when different parts of the tongue or lips are used. Curl your tongue one way, she says, and you sound like the American cartoon duck hunter Elmer Fudd saying: 'Be wawy wawy quiet!' which will not impress new clients at a presentation.

Once her students know what needs to be done to change their flawed speech patterns, Heffley reminds them of the importance of listening, not only to others, but to themselves, by taping their conversations on the phone.

She also introduces them to 'jazz chants', which by listening to the rising and falling intonations, they can learn the pace of English and how to emphasise word meanings through pitch and tone. Other techniques, used by actors, show them how to project their voices.

Heffley's students are of various ages, both sexes (although there are more men than women), and all are keen to learn. 'When a corporate representative calls to discuss enrolling an employee, I always ask if they have discussed this with the employee, and how the employee feels about taking a communication-skills improvement programme,' she says.

'If it hasn't been discussed with the employee, I suggest ways they can approach the individual so it's seen as a positive referral. If the referral was discussed, and the employee's unhappy, I suggest the company have the employee talk with me about the programme, so they understand what we do.

'Usually, if a company is willing to invest training money in an employee for improved speaking skills, it's because they value that person. But they will only keep them if the employee themselves sees a future with promotions. And as a person is promoted, the requirements for good communication increase.'

Fees for the course which can run to 10 weekly meetings of two hours each, range from US$950 to US$1,600 per person, whether for a private individual or corporate employees. Heffley says she prefers small groups and tries to limit them to five people.

Asked to reveal her favourite accent, Heffley diplomatically declines. 'We all have accents, so I try not to be too judgmental,' she says. 'I like just about anything as long as the clarity is good. My biggest complaints are mumblers, and educated people who massacre the language.'

We know at least one very senior US government employee who might fit that description. He often complains that people 'misunderestimate' him. Maybe he could start yesterday.