But the commission on Friday (23 October) rejected the idea, telling reporters it would be counter-productive.

A commission spokesperson said any such moves "would inevitably lead to the United States to impose visa requirements on all EU citizens."

He said the four EU states had made some progress in terms of getting the US visas waived, noting some are close to achieving the objective.

"None of them has asked the commission to temporarily suspend visa free travel for US citizens and they all agree to continue this dialogue ," he said.

But MEPs are unlikely to be happy with the response.

In a recent resolution, they said the commission should have already proposed suspending US visa waivers four years ago.

They want visas imposed on US nationals for at least 12 months, citing EU legislation that requires the commission to act - given Washington has refused to freely admit EU citizens from the four member states.

Spanish socialist MEP Juan Fernando López Aguilar, who steers the EU parliament on the debate, described the US imposed visas as unacceptable.

"The discrimination that Bulgarians, Croatians, Cypriots and Romanians experience when travelling to the US is unacceptable," he said, in a statement.

Similar demands were made by the European Parliament in early 2017.

Poles at the time also required entry visas to the US.

This restriction was then lifted last year, leaving Bulgaria, Croatia, Cyprus and Romania as the only remaining EU states that require a US visa.