The European Union's top official has said the bloc was ready to work "day and night" to reach a post-Brexit trade deal with Britain by the year-end deadline.

Speaking during her first official visit to Dublin, European Commission chief Ursula von der Leyen said that formal talks would begin at the end of February or early March and simultaneously cover a range of issues.

"We are in a very good spirit to go as fast possible, to work as hard as possible day and night to move forward quickly," she said before heading into talks with Taoiseach Leo Varadkar.

"We will go in parallel. It's not only trade. A lot of topics need to be" covered, she added.

Mr Varadkar said that there has to be a level playing field in the Brexit negotiations to ensure that the single market and customs union are "not diluted".

He said there must be a common minimum standard so the United Kingdom does not attempt to "undercut" the EU over its labour and environmental standards.

Mr Varadkar said the Brexit negotiations have reached the halfway point, adding that the next step is to negotiate a free trade agreement between the UK and the EU.

Speaking in Government Buildings this evening, Ms Von der Leyden said the UK will leave the EU in two weeks.

"There's almost no other country in the European Union that is more affected by this decision than Ireland," she added.

"That's why Ireland and Northern Ireland were one of our top priorities during the withdrawal negotiations.

"We do not want a hard border, we delivered that. We've said that Ireland will stay at the heart of the European Union.

Last week, Ms Von der Leyen warned in London that it was "basically impossible" to get a comprehensive free trade agreement negotiated in less than a year.

British Prime Minister Boris Johnson has until 1 July to ask for more time but has vowed not to prolong a process that began when Britons backed Brexit in a 2016 referendum.

The first big clash will revolve around the sequence in which the various issues are discussed. The EU primarily exports goods to Britain and imports British services.

Both sides would like their concerns addressed first in the limited timeframe.

Ms Von der Leyen said negotiators would only really have just eight months because an agreement would take one or two months to be ratified by the various governments.

The talks formally begin after a period of consultations in Brussels and the approval of a formal EU negotiation mandate.

"We're going to be ambitious and we want to have a very close partnership with our British friends," she said.

The overarching theme of the talks will be how closely Britain remains aligned to EU rules and regulations after Brexit.

Ms Von der Leyen insists that Britain cannot expect a preferential trade terms without accepting "a level playing field".

Britain would like to set its own rules after Brexit and strike its own trade agreements with the United States and other economic powers.

"It is the UK's choice," Ms Von der Leyen said.

"The UK knows the closer they want to be to the single [EU] market, the more of course they have to align to the rules of the single market."

Additional reporting PA