STRASBOURG, France, Sept. 12 (Xinhua) -- Jean-Claude Juncker, President of the European Commission, spoke warmly of the future relationship between the European Union(EU) and Britain post-Brexit in his State of the Union Address in Strasbourg on Wednesday.

"After 29 March 2019, the United Kingdom will never be an ordinary third country for us," Juncker reassured the members of the European Parliament, who are meeting in Strasbourg for a plenary session. "The United Kingdom will always be a very close neighbour and partner, in political, economic and security terms."

"In the past months, whenever we needed unity in the Union, Britain was at our side, driven by the same values and principles as all other Europeans," the European Commission President said. The EU and Britain notably shared the same stance regarding recent tensions with the United States over protective trade tariffs imposed by Washington.

"This is why I welcome Prime Minister May's proposal to develop an ambitious new partnership for the future, after Brexit," Juncker told MEPs.

"We agree... that the starting point for such a partnership should be a free trade area between the United Kingdom and the European Union," he added.

The European Commission President's positive tone was counter-balanced, however, by reminders of critical negotiating points, such as access to the single market, and the Northern Irish border issue.

He warned that the EU would be "very outspoken" if ever the British government neglected its obligations under the Good Friday Agreement, which has established peace in Northern Ireland since 1998.

"It is not the European Union, it is Brexit that risks making the border more visible in Northern Ireland," he said.

Reiterating that a third country could not enjoy the benefits of an EU member state, Juncker reaffirmed that Britain would not have access to the single market, and would not be able to cherry-pick parts it wanted.

The State of the Union Address was Juncker's last as he enters into the last 12 months of his presidency, leading up to 2019 European elections.

Brexit, approved by a referendum in June 2016, will see Britain leave the EU and become a third country on March 29, 2019.