Shareholders in both companies interviewed by Bloomberg said there was still likely to be some room for a sweetened offer before a May 22 cut-off.

Steelmakers have raised concerns with Australian authorities that BHP could become too dominant in the global supply of coking coal.

The proposed $39 billion combination has more than enough components to trigger intense oversight by regulators concerned about implications for market concentration and access to key minerals.

Coal India’s stock has nearly doubled over the past year.

It is the first time this has happened in any month in more than four years.

The US, UK, Germany, France, Canada, Japan and Italy agreed on the date after talks on Monday held under Italy’s presidency.