The European Union is getting frustrated with Britain’s strategy in the ongoing Brexit negotiations.

On Friday, chief EU negotiator Michael Barnier warned Britain it had only two weeks to clarify its so-called "divorce payment."

This refers to the money Britain will pay the EU to offset the end of its funding of EU programs and the post-Brexit gap in the EU budget.

Still, with most estimates suggesting the payment will be in the region of $75 billion, the British government is reluctant to put a pen to the checkbook absent concessions from the EU.

Barnier wants to alter that expectation and get something for nothing. Instead, the EU negotiator is determined to provide a substantive update to the European Council at its next meeting in December.

So, what happens next?

I suspect British Prime Minister Theresa May, and Brexit Secretary David Davis will agree on a payment, but only if the EU grants concessions in other areas. Davis is likely asking the EU to give commitments of amenability to a free trade deal and to drop their push for ideas such as the creation of a new border in Northern Ireland.

As Davis put it in regard to that border idea, "We respect the European Union desire to protect the legal order of the single market and the customs union, but that cannot come at cost to the constitutional and economic integrity of the United Kingdom."

Ultimately, however, I’m still optimistic about Brexit’s medium- to long-term outcome. It’s not just that Britain has escaped a deeply undemocratic, inefficient, and arrogant organization. Rather, considering that the UK imports far more from the EU than it exports to the EU, both sides have vested interests in a good trade deal.

The operative question is whether EU leaders will accept that economic rationale or continue seeking to punish Britain for abandoning their auspicious project.