NEW YORK (From news reports) -- Brazilian pulp and paper company Suzano has been in talks with its advisers about sweetening its $15 billion acquisition offer for International Paper, people familiar with the matter said on Monday.

Reuters reported earlier this month that Suzano had approached International Paper to verbally express interest in an all-cash acquisition that was worth roughly $42 per share. Such a deal is conditional on International Paper abandoning its agreement to acquire British packaging firm DS Smith for $7.2 billion.

International Paper rejected Suzano's initial approach, and Suzano is discussing raising its offer by a few dollars per share, one of the sources said.

The sources cautioned there is no certainty that a new bid from Suzano would succeed and asked not to be identified because the matter is confidential.

Suzano, International Paper and DS Smith did not immediately respond to requests for comment.

Suzano's acquisition overtures risk disrupting International Paper's campaign to convince its shareholders to back the DS Smith deal. International Paper will set a date soon for its shareholders to vote on the DS Smith transaction.

International Paper's shares jumped more than 1.3% during market hours on the news on Monday, and further extended gains in trading after the bell. Shares of Suzano, which has a market value of 67.1 billion reais ($13.15 billion), closed up more than 1% in Brazil.

Earlier in May, Suzano's outgoing Chief Executive Walter Schalka said the company's management "will not do anything that could put the company at risk", without commenting on its talks with International Paper.

Suzano is in the middle of a CEO transition. It has tapped Joao Alberto Fernandez de Abreu, the former head of rail operator Rumo, as its new CEO to replace Schalka, who has led the company for 11 years.

Suzano's interest in International Paper comes at a time when the global packaging industry is consolidating. Last year, Ireland-based Smurfit Kappa agreed to combine with U.S.-based WestRock in a deal worth $20 billion.