Business travel to the United States for European company

My Company (based in Germany) has been awarded a project (4 weeks) in the United States for an American client.

Three of us will go, all with European passports on the Visa Waiver Program. we can all get ESTAs without any issues, and I actually have one still valid from last year.

However, I cannot find a definite answer whether we are allowed to work for our European company for an American client, on American soil. All references seem to focus on long-term or remote work.

As Europeans, do we need specific visas to be employed by our European company but work short-term in the USA?

As a follow-up question, what should we tell immigration when we land? I know they usually ask questions about purpose of the trip etc.

EDIT: The purpose of the trip is a risk assessment in the Client's plant, which amounts in layman terms to 4 weeks of business meetings.

EDIT 2: I am currently on my trip, and even though some contact information was outdated (e.g. address in the U.S.), at the airport (Pittsburgh) the process was really simple and was let through without any hassle.

I do confirm the issue about "working" vs. "doing business" as we shortly visited the Canadian side of Niagara Falls. On the way back, the officer asked us what we were doing in the U.S. and looked horrified at my colleague saying "working for an American Client". I saved the day, thanks to you guys, explaining that we were just there for business and our salaries were 100% from our company back in Germany.

Best Answer

Yes, you can!

What you will be looking for would be a B-1 in lieu of H-1B exception:

This exception applies to otherwise-qualified applicants who seek to enter the US to perform professional services. These would-be entrants are not allowed to receive remuneration from a US source (other than an expense allowance or reimbursement) and must be customarily employed by a non-US firm that will continue to pay their salary during the temporary assignment in the US. This provision is referred to as the ‘B-1 in lieu of H-1B’ exception, and is often used by consultants of all varieties who travel to the US to perform short-term professional services on behalf of their UK employers. Although in a May 13, 2011 letter to a US Senator the Department of State indicated that it plans to revoke or at least ‘substantially amend’ the regulation that establishes the B-1 in lieu of H-1B visa, for the time being the visa is still available.

You can find a longer discussion of the details on https://en.wikipedia.org/wiki/B_visa_in_lieu_of_other_visas#B-1_in_lieu_of_H-1B and lots of US immigration laywer websites.

Please note that qualified applicants means qualified for Visa Waiver as opposed to qualified to do their job. This is easy to misunderstand.

Note that it is extremely important that you will not get get paid by the US company but by your home company for the work you will be performing in the US.