OTTAWA/FARNBOROUGH, England, July 13 (Reuters) - Canada said on Wednesday it wanted to move quickly to buy a new fleet of fighter jets but gave no details, leaving major questions about what plane Ottawa will buy as well as how and when.

The previous Conservative government announced in 2010 it would buy Lockheed Martin Corp’s F-35 to replace Canada’s aging CF-18s but later scrapped the decision.

Subsequent efforts to choose a plane stalled and the Liberal government, which took power last November, says it wants to start again.

Defence Minister Harjit Sajjan told reporters on Wednesday there was “an urgent need” to replace the CF-18s, saying a decision on how to proceed would be made within months. He gave no details.

Late last week the government sent out a detailed questionnaire to five potential suppliers and asked them to reply by July 29.

“No decision has been made at this time and all procurement options are being considered,” said the document, which was seen by Reuters.

U.S. and European industry sources said the July 29 deadline was very tight by defense procurement standards, adding they did not know what Ottawa intended to do with the results of the questionnaire.

One option is unveiling an open competition - which a European industry source said “would cost millions” to participate in - while another is announcing a sole-source order for one of the jets.

Another source familiar with the process said Canada was unlikely to reach a decision and pick a winning bidder until next year at the earliest.

The five potential suppliers are Lockheed Martin, Boeing Corp, Eurofighter, Saab AB and Dassault Aviation SA. Sajjan’s officials have denied reports saying Ottawa has decided to buy Boeing’s Super Hornet as an interim measure.

Although the Liberals vowed during last year’s successful election campaign to hold an open competition and said they would not buy the F-35, it is notable that Ottawa is talking to Lockheed Martin.

Pentagon acquisition chief Frank Kendall said at the Farnborough Airshow on Sunday he believed the Canadian military preferred the F-35.

The Canadian questionnaire stresses the winner must provide considerable work to domestic firms. Canada is one of the nine original partner countries that helped fund development of the F-35.

Lockheed Martin has said Canadian firms would account for work on the program worth about $1 billion by end-2016 but added that this could be at risk if Ottawa buys another jet. (Writing by David Ljunggren)