Seven months after the referendum to leave the EU, Brexit "still has not been formalized," said Frank-Walter Steinmeier in a statement.
"We therefore welcome the fact that the British prime minister has today sketched out her government's plans for leaving and finally brought a bit more clarity about the British plans."
Steinmeier said May had "underlined that Britain aims to have a positive and constructive partnership, a friendship, with a strong EU".
"That is good," he said. "We also want as good, close and trusting a relationship as possible and hope for constructive negotiations with this goal."
He stressed though that Berlin would not enter into talks on the terms of Brexit until Britain triggers Article 50 of the Lisbon Treaty, officially declaring the country's intention to quit the EU.
"Our position is and remains: negotiations will only begin when Britain has officially announced its desire to leave," Steinmeier said, adding that a parliamentary committee devoted to Brexit would meet to chart its course for the talks.
However he underlined the interest of "Germany and Europe in strengthening the cohesion of the European Union of 27 members and the unity of the European single market".
May on Tuesday said Britain would leave the EU's single market in order to restrict immigration in a clean break from the bloc but would seek a trade deal giving "the greatest possible access" to the market on its departure.
However, other German politicians were critical of her speech, with Green Party MEP Jan Albrecht saying that both Leave and Remain voters would suffer from leaving the single market.
"May is blatantly making fun of her electorate!" he said in another Tweet.
#May: Go fuck yourself EU but please don't let us down. *whine* *whine*— Jan Philipp Albrecht (@JanAlbrecht) January 17, 2017