German chemicals group BASF has lined up a loan package from large multinational banks for a potential takeover offer for Syngenta, the Swiss crop chemicals maker, but will bide its time, several people familiar with the matter said.

Syngenta has already rejected a $45 billion takeover approach from Monsanto, which wants to combine its seeds business with the Swiss group's pesticides activities.

"BASF has committed financing in place to buy Syngenta," one of the people said, asking not to be identified because the negotiations are confidential.

BASF and Syngenta declined to comment.

A takeover of Syngenta by BASF would be likely to face significant antitrust issues but could also prevent the seeds and pesticides market being reshaped by rivals.

"BASF has no interest in the Monsanto-Syngenta deal going through. It would make Monsanto the absolute number one in crop protection and seeds," an industry banker said.

Analysts estimate that U.S. group Monsanto's global market share in seeds and crop chemicals would be 26-29 percent after a merger with Syngenta, including proposed antitrust remedies. That would be up from about 16-17 percent currently.

BASF will only decide to submit a bid for Syngenta if Monsanto makes a formal offer for the Swiss group, the sources said, adding that BASF was comfortable with there being no merger at all which would preserve the industry status quo.

Sources have previously told Reuters that BASF could also buy Syngenta's seed business, which Monsanto said it would shed to allay antitrust concerns if a Monsanto-Syngenta deal were to go through.

But a combination of BASF and Syngenta without Monsanto's involvement would also face major antitrust issues, especially in fungicides and in Europe, analysts have said.

"BASF will not be a first mover but remain a reactive player," one of the people said.

The person also said that while BASF had secured roughly $50 billion in bridge financing, the company would be likely to eventually finance a deal with roughly $30 billion in debt while paying for the rest with cash and newly raised capital.

"After a potential bid, BASF may also opt for loading some of that debt onto Syngenta," the other source said.

Reuters reported in June that BASF was considering a potential offer for Syngenta.

BASF, the world's largest chemicals group by sales, is developing improved plant characteristics such as drought tolerability but relies on partners, the biggest being Monsanto, to bring finished seed products to market.

BASF's crop chemicals division with 5.4 billion euros ($5.9 billion) in 2014 sales, commands about 11 percent of the global crop chemicals market, putting it in third place behind Syngenta and Bayer.

Syngenta has refused to open its books to Monsanto even though the U.S. company has offered to make a $2 billion cash payment should the transaction fail to win regulatory approval.

"We said no in 2011, we said no in 2012, we said no in 2015. What part of no don't they understand?" Syngenta Chief Executive Michael Mack said last month.