"I welcome publication of UK proposal on customs aspects of IE/NI backstop," he tweeted, referring to the land border between the British province of Northern Ireland and EU member Ireland.
"We will examine it with 3 questions: is it a workable solution to avoid a hard border? Does it respect the integrity of the SM/CU? Is it an all-weather backstop?"
EU negotiators have rejected previous British proposals on the grounds that time limits for finding other solutions were not acceptable and that applying a new customs and economic regulation deal to the whole of Britain and not just Northern Ireland could be a "backdoor" way for Britain to keep access to EU markets without being subject to all the EU's rules.
London rejected a backstop proposal from Barnier in December which would keep Northern Ireland within much of the EU's regulatory system on the grounds that this would create new barriers between the province and the British mainland.