"Of course, we are not going to have completely frictionless trade because we have left the [EU] customs union and single market", he said.
The United States is the UK's second-largest trading partner secondary only to the European Union, but as the UK seeks to impose digital taxes on US tech companies and the USA threatens to impose tariffs on British vehicles, the two parties have a long way to go to complete the free trade negotiations.
The EU insists on a "level playing field" so that Britain does not try to get an unfair trading advantage by getting rid of costly EU standards on labour, the environment and taxes.
Von der Leyen said it was "not the time" to lower standards or be "lukewarm" on the climate crisis. We are now trading on WTO terms.
Mrs von der Leyen added that the European Union and Australia were planning to agree a better free trade agreement which would remove some of the tariffs that come with WTO terms.
If there was no agreement by the end of the year, the United Kingdom would leave the Single Market and Customs Union and trade on WTO terms with the EU, he said.
"If we fail to reach an agreement there will be quotas and tariffs on all British produce", he said, "That's the result if we fail to reach that agreement within the constraints set by the British prime minister".
Criticising Johnson's proposal she said that "Australia is a strong and like-minded partner, but the European Union does not have a trade agreement with Australia, " adding "we are now trading on World Trade Organization terms".
In addition, for economies that already have a free trade agreement with the European Union, the United Kingdom needs to renew the negotiations; for those that have not yet inked a free trade deal with the European Union, the country can also get the negotiations in gear after Brexit.
Von der Leyen noted that the "Canada-style deal" referred to by Johnson as his primary goal in the coming negotiations contained tariffs and quota limits on some goods crossing the Atlantic.
Northern Ireland could be forced to operate in a different time zone from the rest of the UK for half of the year under Boris Johnson's Brexit deal, the UK Parliament's EU Internal Market Sub-Committee has warned in a recent report. "The right to diverge will come at a cost, a very heavy cost". "This includes negotiating strong guarantees to ensure fair competition and high common standards".
Von der Leyen said she was surprised, however, that Johnson recently mentioned the "Australian model", as the European Union does now not have a trade agreement with Australia, but was looking to change that.
Before we build on the ideas behind how Brexit may affect the property investment market, it's important to discuss the approach on how the UK's Prime minister has meant to leave the European Union.
Mutual trade ambition and a suitable agreement would "trigger an upward dynamic competiton" that would benefit both parties, she said, before handing the floor over to European lawmakers.