A refusal by the U.S. to clarify when it would remove punitive trade measures against the European Union is a key reason the transatlantic allies failed to reach an accord on steel trade this week that would have resolved a Trump-era dispute, according to the bloc’s chief trade negotiator.

Valdis Dombrovskis, an executive vice president at the European Commission, said the U.S. previously agreed to work toward removing so-called Section 232 tariffs that hit more than $6 billion of EU steel and aluminum exports in 2018 as well as tariff-rate quotas that were introduced later as part of a temporary truce.

"The main stumbling block was absence of clarity from the U.S. side on a clear timeline and how the 232 tariff-rate quotas would be removed,” Dombrovskis said in an interview Friday following a summit in Washington. "Unfortunately, we have not seen a strong commitment and engagement from the U.S. side to make sure those tariffs” are being removed."