Monsanto has reportedly upped its offer for Swiss agro-chemical giant Syngenta.

An anonymous source told news agency Reuters that Missouri-based Monsanto, the world’s largest seed company, has raised its offer for Syngenta to $47 billion (around £30 bn), after an earlier offer of $45 bn (£29 bn) was rejected in June.

In June, Syngenta high-ups said that Monsanto’s plans to float off certain overlapping assets if it does acquire the chemical firm are not enough to address serious anti-trust concerns that are likely to arise in several countries in which the firms currently trade.

Syngenta executives told their shareholders that Monsanto’s second offer represented the “Same inadequate price, same inadequate regulatory undertakings… same regulatory risks and same issues associated with dual headquarters’ moves” as the first offer of this year, which Syngenta turned down in May.

Syngenta, which is headquartered in Basel, has refused to open its books to Monsanto and rejected an initial offer of a $2 bn (£1.27 bn) cash payment should a merger fail to gain regulatory approval. Monsanto has also reportedly increased the offer of a break-up fee to $3 bn, according to Reuters’ source, said to be close to the process.

Neither company has commented on the matter.