LONDON -- Three weeks before Britain is due to leave the European Union, the president of the European Commission warned Wednesday that the U.K. won't get the "highest quality access" to the European Union's market after Brexit unless it makes major concessions.
In a friendly but frank message to the U.K., Ursula von der Leyen said negotiating a new U.K.-EU trade deal will be tough. She also said the end-of-2020 deadline that British Prime Minister Boris Johnson has imposed on negotiations makes it "basically impossible" to strike a comprehensive new agreement in time.
Von der Leyen, who took over as head of the EU's executive branch on Dec. 1, met Johnson at 10 Downing Street in London on Wednesday for the first time since the British leader's election victory last month.
Johnson's Conservatives won a substantial parliamentary majority in Britain's Dec. 12 election, giving him the power to end more than three years of wrangling over Brexit and take the U.K. out of the EU on Jan. 31. It will be the first nation to ever leave the bloc, which currently has 28 members.
Britain's departure will be followed by a transition period in which the U.K.-EU relationship will remain largely unchanged while the two sides negotiate a new trade arrangement.
Johnson says the U.K. is seeking a wide-ranging free trade deal, but doesn't want to agree to keep EU rules and standards. Britain wants to be free to diverge from EU regulations in order to strike new trade deals around the world.
Johnson's office said the U.K. planned to base its trade negotiating stance "on an ambitious FTA (free trade agreement), not on alignment."
That could cause problems. Speaking at the London School of Economics before her meeting with Johnson, von der Leyen warned that "without a level playing field on environment, labour, taxation and state aid, you cannot have the highest quality access to the world's largest single market."
"With every choice comes a consequence. With every decision comes a trade-off," she warned.
International trade agreements typically take years to complete, but Johnson has ruled out extending the post-Brexit transition period beyond the end of 2020, although the EU has offered to prolong it until 2022. Downing Street said Wednesday that "both British and EU citizens rightly expect negotiations on an ambitious free trade agreement to conclude on time."
Von der Leyen said the time frame was "very, very tight" and made it "basically impossible" to negotiate anything but a skeleton deal.
"The more divergence there is, the more distant the partnership has to be," she said. "And without an extension of the transition period beyond 2020, you cannot expect to agree on every single aspect of our new partnership. We will have to prioritize."
The German EU chief -- who studied in Britain in the 1970s and has proclaimed herself a friend and fan of Britain -- did have some encouraging words for Johnson. She said the bloc was ready to strike a tariff-free and quota-free trade deal with Britain, and "a partnership that goes well beyond trade and is unprecedented in scope."
She said the new relationship could encompass "everything from climate action to data protection, fisheries to energy, transport to space, financial services to security. And we are ready to work day and night to get as much of this done within the time frame we have."
At the start of the meeting, Johnson noted that he and von der Leyen had attended the same Belgian school -- the European School in Brussels, where both lived for a time as children. Johnson, 55, is six years younger than the EU chief.
Johnson joked that when he was at the school, he and his friends "introduced a very rough game called British Bulldog."
Johnson's election victory broke Britain's political stalemate over Brexit. His 80-seat House of Commons majority means he has the votes to get his Brexit deal approved by lawmakers, something his predecessor Theresa May never achieved. It also means pro-EU lawmakers can no longer change or block legislation as easily as they did under May's minority administration.
Johnson's key Brexit bill was approved in principle last month and is expected to pass its final House of Commons hurdle on Thursday after three days of debate. It also must be approved by the European Parliament.
Von der Leyen said she did not anticipate a delay and expected the U.K. to leave the EU on Jan. 31.
"This will be a tough and emotional day," she said.