Foreign Secretary Boris Johnson said Mrs May's "powerful" speech will be "well received" by EU nations.
Speaking to reporters at Lancaster House, he went on: "Because it's negotiable, this is something that I think will be good for the UK and good for the rest of the EU as well."
Asked why the EU would give the UK a "free lunch", Mr Johnson said: "As the Prime Minister said, I think it's going to be good for both sides."
He went on: "We very strongly think this is in our mutual interest. We're not leaving Europe, we're disentangling ourselves from the treaties of the EU.
"We can remain powerfully committed to Europe with a new European partnership ... whilst also going forward with an identity as Global Britain."
Jeremy Corbyn has accused Theresa May of producing a "bargain basement Brexit" plan and "demeaning" the UK's European standing.
Following Theresa May's announcement of her plans for Brexit, how have newspapers across Europe and the UK reacted?
The Prime Minister said Parliament will be given a binding vote on the final deal, but said the result will not stop Britain leaving the EU.