UK warns EU on Brexit: We won't blink first

"We came in after a government and negotiating team that had blinked and had its bluff called at critical moments and the EU had learned not to take our word seriously," negotiator David Frost told the Mail on Sunday, Reuters reported.

"So a lot of what we are trying to do this year is to get them to realize that we mean what we say and they should take our position seriously," he was quoted as saying.

Britain became the first country to leave the EU last January and is now in a standstill transition period to allow both sides to agree a new deal on everything from trade to security to nuclear cooperation.