European Union countries will discuss and likely vote on Thursday on measures proposed by the European Commission to curb steel imports into the bloc, EU sources said.

The Commission has proposed a combination of a quota and a tariff to prevent a surge of steel imports that is threatened, notably since the United States imposed levies on incoming steel and aluminium.

The quota would be a reflection of imports over recent years, with a 25% tariff set for volumes exceeding that amount, according to sources familiar with the proposal.

The main exporters of steel to the EU are China, India, Russia, South Korea, Turkey and Ukraine.

The European Commission, which oversees trade policy for the 28-member EU, launched a study in late March into whether US import tariffs warranted action to prevent mainly Asian producers flooding Europe with steel.

The US tariffs of 25% on incoming steel and 10% on aluminium came into effect on March 23 and have also been imposed on EU producers since June 1.

The investigation covers 28 steel grades and products made with steel, with the Commission noting at the launch of its investigation that imports of the steel products concerned rose from 18.8-million tonnes in 2013 to 30.6-million tonnes in 2017, far higher than the increase of domestic production.

The investigation into steel is provisionally set to last nine months - meaning until the end of the year.

But, under Word Trade Organization (WTO) rules, the EU can impose "provisional safeguard" tariffs for up to 200 days if it makes a preliminary finding that increased imports have caused or are threatening to cause serious injury to its steel sector.

EU Trade Commissioner Cecilia Malmstrom said last month that provisional safeguards could possibly be set in place in July.

The EU has also imposed its own tariffs on 2.8-billion euros ($3.3-billion) of US imports, including bourbon and motor bikes, and has launched a legal challenge at the WTO.