PATRICK Harvie has said he expects to unveil a potential joint government deal with the SNP “very soon”, but still wants Nicola Sturgeon to “go further” on climate change.

The Scottish Greens co-leader also said the potential agreement would have to be put before Green party members before it could be finally signed off. 

However he appeared optimistic that a deal would be struck, paving the way for the first Green ministers since the start of devolution.

Ms Sturgeon announced she had opened talks with the Greens on a joint government deal short of a formal coalition at the start of the summer.

With the First Minister due to set out her legislative programme for the year on August 31, a deal has to be confirmed within the next few days.

If ratified, it would be the first time the SNP has shared power since coming to office in 2007, having twice governed as a minority and once as a majority.

The party won 64 MSPs at the Holyrood election in May, once short of a majority, while the Greens had eight before Alison Johnstone then quit to become Presiding Officer.

Ms Sturgeon does not need the seven remaining Green MSPs to govern, but the addition of another pro-independence party could increase pressure on Boris Johnson to grant Indyref2, although the two parties also disagree on fundamental aspects of independence, including the move to a new currency.

It would also burnish Ms Sturgeon’s environmental credentials ahead of the COP26 climate summit in Glasgow in November.

However the two parties are currently at loggerheads over the propsoed Cambo oilfield off Shetland, which the Greens detest but which Ms Sturgeon has yet to oppose.

The First Minister last week asked Mr Johnson to “reassess” the licence for the Cambo field ahead of COP26, but conspicuously stopped short of criticising it herself.

Asked on Radio Scotland’s Sunday Show about the progress of the talks, the Glasgow MSP said: “Everybody is very keen to know the outcome. I don’t think you have very long to wait. 

“I’ve got party members as well who really want to know what’s happening here. 

“They’ll get a vote at the end of this if we do agree something with the SNP. 

“It won’t be put into practice until our party members have had a vote.”

“I hope very soon that we’ll be able to publish something.”

The Glasgow MSP said that in the last Holyrood term the Greens had pushed the SNP “out of their comfort zone” and a deal could do that “in a more coherent way over the long-term”.

He said: “We absolutely should be looking at how we can maximise that opportunity.”

He said a constructive opposition achieved far more than an “opportunistic” one.

Asked about the First Minister asking the PM merely to reassess the Cambo licence, Mr Harvie said: “It’s an important first step. It’s not where we need to end up, no. It’s not the end of the journey. It’s an important first step.

“Labour as well have been wedded to this idea of maximum economic extraction for many many years. They’re now saying Cambo shouldn’t go ahead. 

“Across the political spectrum you are starting to see people finally recognise what the Greens have been saying for many, many years - that we have more oil and gas in existing reserves than we can afford to burn if we’re remotely serious.”

Asked if he agreed with Greenpeace and Friends of the Earth that Ms Sturgeon was “hiding behind the Prime Minister”, Mr Harvie said: “She hasn’t said it should stop. 

“I think we want to see that kind of position taken right across the political spectrum, not just by the SNP but by all political parties. 

“There are responsibilities for every political leader to go further, and I think people will go further than the First Minister has gone so far.”

Asked if the Greens could do a deal with a party that didn’t oppose Cambo, he said: “We’re going to be pushing as fast and far as we possibly can on all political parties to go further than they have on this issue.” 

Asked about possible the ministerial posts he and fellow co-leader Lorna Slater are tipped to fill, Mr Harvie said: “The First Minister was open to that as a posssibility.

"But we’re trying to get to a point where we’ve reached agreement on some issues which… are difficult.

“Political parties trying to push one another in a constructive way to change long-standing polices, that’s a difficult conversation. 

“So it wouldn’t be right for me to start laying out specific details now.

"I don’t think you’ve got very long to wait, and I hope if we do manage to see this that people right across the political spectrum will see that this is the way that political parties make a difference.”

The Tories have warned an SNP-Green deal would be a "coaltion of chaos", and warned it could lead to job losses in the North East in the oil and gas industry.