Summit Materials, the Denver-based construction materials company, has made a rival bid to buy US supplier Ash Grove Cement, financial news service Bloomberg reports.
The move has put Summit in competition with the $3.5 billion takeover offer from Irish building materials firm CRH.
Summit Materials made a last-minute proposal to combine with Ash Grove, according to people familiar with the matter.
Kansas-based Ash Grove last night said the offer from a third party, which it did not identify, was valued at $3.7 billion to $3.8 billion.
Ash Grove's board said the offer could result in a superior proposal and that it would engage in talks with the third party.
CRH reiterated in its own statement today that it had agreed to acquire Ash Grove for $3.5 billion and said the period for obtaining shareholder approval has been extended.
CRH said it plans to monitor the situation for now, though it has the capacity to raise its offer if it decides to do so, sources said.
The move by Summit Materials founder and chief executive Tom Hill, who previously worked at CRH, is ambitious because the company, valued at $3.6 billion, would be trying to buy a company that is almost the same size.
This could raise questions about how the US firm can finance such a bid and whether it would be a share deal, compared to an all-cash offer from CRH.
Summit's net debt is currently 4.4 times EBITDA as against 2.1 times for CRH, according to data compiled by Bloomberg.
"The outcome of the bidding process will likely come down to a question of whether the family-controlled Ash Grove wishes to stay in the industry merged with Summit or alternatively take the cash offer from CRH and exit," said David Holohan, chief investment officer at Dublin-based Merrion Capital.
"Given CEO Tom Hill's intricate knowledge of the sector and given his history of running CRH's US business, it is unsurprising to see the company engage in the bidding process for Ash Grove," the analyst added.
CRH agreed last month to buy Ash Grove, which is majority owned by the Sunderland family and has called the Irish producer its largest customer.
The deal was the latest sign of global consolidation among building-materials suppliers, coming the same week as Germany's HeidelbergCement agreed to buy Italian assets from Cementir Holding.
The counter proposal from Summit throws a spanner in the works for CRH, a serial buyer and seller of assets which announced in August the disposal of a division for $2.63 billion.
CRH's plan "has been disrupted by the emergence of an 11th hour bidder," Davy said in a note today.
"That development is perhaps not surprising given Ash Grove's attractive position in the US cement market," the stockbrokers added.
Ash Grove operates eight cement plants across eight US states. Last year it reported profit before tax of $215m and gross assets of $2.5 billion.
CRH would receive a termination fee of $131m if Ash Grove breaks the agreement, according to the merger documents.
Shares in CRH were lower in Dublin trade today.
