The Chicago Fire have increased their contract offer to former Chelsea striker Didier Drogba, a source with knowledge of negotiations said on Tuesday.

Last week, a source told ESPN FC that the MLS club had offered Drogba an 18-month contract worth $2.5 million a year, but Chicago have now upped the money in the potential deal.

The club also confirmed negotiations were ongoing with the Ivorian international.

"The Chicago Fire are interested in signing Didier Drogba and have been in direct contact with the player and his agent to negotiate a contract," said club vice president Doug Hicks in a statement.

"We would love to have Mr. Drogba join our club and we are working within the rules set by Major League Soccer for the discovery process.

"In accordance with those rules, it is inappropriate for anyone outside our club to infringe upon this process."

The Fire have been trying to fend off interest from an unidentified Qatari club, and on Monday the Montreal Impact told TVA that they are also negotiating to bring the 37-year-old to MLS.

TVA reported that the Fire have priority to sign the 37-year-old, but Drogba would prefer Montreal, where he can speak his native French.

Chelsea are also operating out of Montreal this week as they prepare for their preseason tour. Jose Mourinho was asked what advice he would give to his former player, and responded in his usual glib manner.

'What can I say? I can say if he doesn't have a house yet the hotel is good to stay. I can say that I saw some nice houses when I went for a walk to the top point. The training ground is good, in very good conditions," Mourinho said.

"And the people love football. If not they would not be at the training ground every day, stopping us every day when we go for a walk. The weather is nice for now but I cannot speak about the winter! The colours of the club are also nice!"

Earlier on Tuesday, Fire chief operating officer Atul Khosla revealed the two sides had been in touch for three weeks.

2/3) Working to get Didier Drogba to #cf97, would love to have him, have been going through discovery process as we have the rights - Atul Khosla (@atulkhosla) July 21, 2015

3/3) Our club has been in regular dialogue over past 3 weeks with Didier Drogba and his representatives #cf97 - Atul Khosla (@atulkhosla) July 21, 2015

Information from ESPN FC reporter Jeff Carlisle was used in this report.