Brussels  - Top EU figures welcomed Thursday the Brexit divorce deal struck with London, even as British Prime Minister Theresa May was battling domestically for the deal's - and her own - political survival.

EU: "decisive progress" had been made

On Wednesday, May's government gave its backing to the withdrawal agreement, leading EU negotiators to declare that "decisive progress" had been made in efforts to secure an orderly departure when Britain leaves the European Union in March.

European Council President Donald Tusk convened an EU summit on November 25 for the bloc's remaining 27 leaders to approve the agreement, as well as a still-to-be finalized political declaration on future relations between Britain and the EU.

German Chancellor Angela Merkel said she was "very glad" that a deal had been struck, after "long and not entirely easy negotiations."

European Parliament President Antonio Tajani said he was satisfied about three key elements of the deal: the protection of EU citizens' rights, British financial commitments and the avoidance of a hard border on the island of Ireland.

The EU legislature, which must ratify the deal, will cast its vote early next year, Tajani added.

Others were more cautious in their assessment of progress.

"Our work is not finished," EU Brexit negotiator Michel Barnier said early Thursday. "We still have a long road, a long road ahead of us on both sides."

The European Commission refused to be drawn on the consequences of Thursday's political turmoil in London.

British parliament must approve the deal

"Our negotiating partner is Prime Minister May and the UK government. We continue to work in good faith with them," spokesman Margaritis Schinas told journalists in Brussels.

Tusk also declined to comment on developments in Britain.

"All I can say is that the EU is prepared for a final deal with the United Kingdom in November. We are also prepared for a no-deal scenario. But of course we are best prepared for a no-Brexit scenario," Tusk said.

Representatives of the 27 remaining EU member states will now analyse the compromise text over the coming days.

The key sticking point in negotiations had been the so-called backstop to keep an open border between the Republic of Ireland, which will remain in the EU, and Northern Ireland, which will leave with the rest of Britain. There are fears of a return to violence should the two be divided.

The draft deal now includes an option to extend the 21-month transition period that kicks in after Britain leaves the EU, as well as a backstop provision that would keep all of the United Kingdom in the same customs territory as the bloc until a permanent arrangement can be found.

This drew some of the fiercest criticism from British eurosceptics, who argued that it would keep Britain tied to the EU while making it impossible for London to unilaterally exit the arrangement.

The British parliament must approve the withdrawal deal for it to take effect.

Without a transitional agreement in place, EU laws would no longer apply in Britain after March 29, 2019, likely triggering chaos and economic pain on both sides.