Boris Johnson will ask for a Brexit delay this week if he fails to secure a deal.

The UK's Brexit Secretary Stephen Barclay confirmed that Johnson would comply with legislation requiring him to seek a third extension if he can't secure a deal.

The admission comes as negotiators in Brussels try to reach an agreement in time for Thursday's European Council summit.

However, EU sources suggest a delay is now inevitable, whether a deal is agreed in principle or not.

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Boris Johnson will write to the European Union requesting that Brexit is delayed, if he fails to agree a deal with Brussels by Saturday, a senior member of his government has confirmed.

The prime minister has repeatedly insisted that there are "no circumstances" under which he would allow Brexit to be delayed, tweeting last week that there would be "no delay."

However, under the terms of a law passed by members of Parliament last month, known as the Benn Act, Johnson would be legally obliged to request a delay if he has failed to pass a deal by October 19.

Asked by a parliamentary committee on Wednesday whether Prime Minister Johnson would request a fresh extension to Article 50 if he fails to secure a deal, Brexit Secretary Stephen Barclay conceded that he would.

"I can confirm as the prime minister has repeatedly set out that the government will comply with the law and secondly it will comply with undertakings given to the court in respect to the law," he told MPs.

Pushed again on whether the prime minister would send the letter, he replied: "I confirm that the government will abide by what was set out."

Read more: Boris Johnson could offer the DUP 'billions' of pounds to support his Brexit deal

Government lawyers have previously acknowledged that Johnson would comply with the Benn Act, which was passed by MPs last month in order to prevent the United Kingdom leaving the EU without a deal at the end of October.

Under the terms of the act, the prime minister must write to the EU no later than October 19 if he has failed to pass a House of Commons vote on a deal by that date.

The admission comes as talks with the EU continue in Brussels over whether a deal can be agreed in time for a European Council summit which will get underway tomorrow and conclude on Friday.

Negotiations continued until the early hours of this morning, before resuming at 09:00 Brussels time.

The DUP could torpedo any Brexit agreement

Hopes of an imminent agreement were raised last night with reports that both sides were "closing in" on a deal.

However, government sources downplayed suggestions of an immediate breakthrough on Wednesday following talks with the Democratic Unionist Party, which props up Johnson's minority government.

The staunch unionist party is reportedly demanding "billions" of pounds in extra funding for Northern Ireland before it will back a deal.

The DUP is adamant that Northern Ireland must stay in the UK's customs union after Brexit.

However, the Guardian reported that under the terms of the agreement being worked towards, the province will remain wedded to EU customs rules after Brexit, if a new trading relationship that preserves the seamless Irish border is not in place.

DUP leader Arlene Foster met with Prime Minister Johnson on Tuesday evening to discuss the agreement.

She told reporters that she would "do what's best for the union."

Failure to secure the support of the DUP would dramatically decrease Johnson's hopes of passing any deal through parliament, where he currently has a majority of minus 45.