OTTAWA (Reuters) - The Canadian government’s plan to legalize recreational marijuana by next July could be in jeopardy, with opposition brewing among some in the Senate and concerns that the deadline to pass the bill is rapidly approaching.

Canada's Prime Minister Justin Trudeau waits for the arrival of Colombia's President Juan Manuel Santos on Parliament Hill in Ottawa, Ontario, Canada, October 30, 2017. REUTERS/Chris Wattie

The Senate’s approval is needed to pass laws though it does not often block bills passed by the elected House of Commons. Some senators say police need more time to prepare and also oppose setting the federal age of legal use at 18.

Legalizing marijuana for recreational use was part of Liberal Prime Minister Justin Trudeau’s 2015 election campaign and the government has set a relatively quick deadline to put it in place. Canada would be the first Group of Seven country to allow the drug nationally.

The legislation is not expected to reach the upper house until December and some senators have said they will take as long as they need to review it.

That could put Trudeau and the upper house of parliament at loggerheads again. Senators, who are not elected, recently delayed the government’s budget bill before ultimately passing it.

Conservative Senator Pierre-Hugues Boisvenu said he expects implementation will need to be delayed until December 2018 or early 2019 to give police forces enough time to prepare for widespread use of the drug.

“I think it’s too early,” Boisvenu said on Friday by phone. “What they’ve (the police) told us until today is they will not be prepared next July.”

Boisvenu said Conservative senators will meet to discuss strategy about delaying the bill if necessary.

Member of Parliament Bill Blair, a former police chief and the government’s point person on the legislation, said added delays in regulation will put more underage users at risk.

“By all means, take the time to do it right, but unnecessary delay is unacceptable,” Blair said by phone.

The potential clash highlights a hurdle Trudeau has partly set up for himself after he expelled all Liberal senators from the party’s caucus in 2014 amid an expenses scandal and to curb partisanship.

Although Trudeau has appointed independent senators since then, he has no formal leverage to get the government’s legislation passed.

“The government, if it had a clear majority in the Senate, could at one point impose party discipline and have its bill voted on. It’s not in that situation now,” said Senator Andre Pratte, an independent who was appointed by Trudeau in 2016.