In Berlin, Ms Merkel's office said it would not comment "on such confidential discussions".
"This has to be on the basis of negotiation where the extent of the problems that are caused by Brexit are recognised, particularly on this island". "At stake is the future of Europe and the United Kingdom".
Talks between Frost and junior European Union officials were to begin later Tuesday, then chief European Union negotiator Michel Barnier was to meet Irish foreign minister Simon Coveney in the evening.
However, a senior Downing Street source has said: "The government will comply with the Benn act, which only imposes a very specific narrow duty concerning Parliament's letter requesting a delay, drafted by an unknown subset of MPs and pro-EU campaigners, and which can be interpreted in different ways".More news: USA pilots sue Boeing for ‘rushing’ unsafe 737 Max into market
Mr Johnson has previously said the government "will obey the law - and will come out on 31 October" in any event, without specifying how he would achieve these apparently contradictory goals. "They hope to meet in person later this week".
On Tuesday, Britain published more details of its plans for a scenario where there is no deal.
On the markets, the pound slipped to its lowest value against the euro in about a month.
The "Readiness Report", for example, notes the government has created a dedicated unit to support suppliers of medical goods in Britain, which could soon need to jump through additional hoops to ensure the integrity of their supply chains.
Johnson, who once said he would rather be "dead in a ditch" than seek a Brexit extension - submitted new plans last week in place of an agreement his predecessor Theresa May struck with Brussels in late 2018.
As a result, a Downing Street source has revealed Mr Johnson is now pursuing a no deal Brexit and will go against any nation that tries to get in his way.More news: United States adds Chinese AI and facial recognition companies to entity list'
On Tuesday, the government suspended the legislature from Wednesday until October 14, when Queen Elizabeth II will set out the government's legislative domestic agenda. "It also made clear that they are willing to torpedo the Good Friday agreement".
Mr Johnson sent new proposals to Brussels last week, with the key focus being on replacing the so-called backstop - the policy negotiated by Theresa May and the European Union to prevent a hard border returning to the island of Ireland - which has always been a sticking point.
Under this proposals, Northern Ireland would leave the EU's Customs area along with the rest of the United Kingdom and the province's institutions would have the power to remain in or to exit the regulatory zone - possibly a step too far for Ireland and the EU.
Finding a way to keep the border open without keeping at least a part of the United Kingdom tied to European Union trade rules has always been the main sticking point in the talks.
French President Emmanuel Macron says the European Union will assess by Friday whether a deal is possible.
Sassoli told Sky News that Johnson said to him that he "will not ask for an extension".More news: City Charges Trump $500K, Obama $20K For Rally Security
The latest comments from Downing Street follow a warning that negotiations with Brussels to enable Britain to leave at the end of October with a deal would "probably" end this week.
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