LONDON (AP) — Britain's Brexit chief has met politicians from both sides of Northern Ireland's political divide in efforts to solve a problem over the Irish border that is frustrating divorce talks between the U.K. and the European Union.

Yet there was little sign of a breakthrough after Brexit Secretary Dominic Raab met Friday with the pro-British Democratic Unionist Party and Irish nationalists Sinn Fein.

Britain and the EU agree that after Brexit there must be no customs posts or other impediments between the U.K.'s Northern Ireland and EU member Ireland. But they don't agree on how to guarantee that.

The DUP, which props up Britain's Conservative government, says there can't be customs checks or anything else between Northern Ireland and Great Britain that "undermines the constitutional or economic integrity of the United Kingdom."