LAVAL -- Valeant Pharmaceuticals International says it will improve its bid of almost US$47 billion for Botox-maker Allergan after the U.S. company rejected its hostile takeover offer.

Valeant CEO Michael Pearson says the company is prepared to pay a fair price, but will remain financially disciplined when it makes its new offer later this month.

Under the current proposal, Valeant, which has teamed up with activist investor Bill Ackman, has offered $48.30 in cash and 0.83 of a Valeant share for each Allergan share. Valeant did not say Tuesday how it would improve the bid.

Pearson said he will tell Allergan shareholders during a presentation on May 28 why Valeant's offer is better than Allergan's "go it alone" strategy and improve the offer "to demonstrate our commitment to getting this deal done."

He is also expected to provide details about Valeant's business strategy and costs savings from its recent transactions and address concerns that Allergan has raised about Valeant's acquisition strategy.

"We are prepared to pay a full and fair price, but, consistent with our track record, we will remain financially disciplined," Pearson said in a letter to Allergan shareholders.

"We will not stop our pursuit of this combination until we hear directly from Allergan shareholders that you prefer Allergan's 'stay the course plan' to a combination with Valeant," Pearson said.

Ackman's Pershing Square Capital Management LP -- Allergan's biggest shareholder at 9.7 per cent -- has agreed to take only stock in the transaction.

Allergan has adopted a "poison pill" defence that will allow it time to consider alternatives and potentially block the bid.

The company has said it can do a better job growing the company alone while also criticizing its Canadian rival's business model.

California-based Allergan has said that its investments in research and development have built a strong pipeline of products that will generate double-digit annual revenue and earnings growth for at least six years.

Allergan noted that it has transformed anti-wrinkle Botox from a $100-million a year product in 1989 to one that generates $2 billion for both its aesthetic and therapeutic uses.

Valeant contends Allergan spends too much on early research and development, saying the proposed takeover will result in more than US$2.7 billion in annual cost savings, 80 per cent of which would be achieved in the first six months.

It said last year's acquisition of eyecare company Bausch & Lomb is an example of removing layers of management while driving higher sales.

However, Allergan said Valeant's estimates don't seem to include some $200 million needed just to maintain products currently on the market.