The operator of the Northern Territory's newest mine has been unable to secure an agreement to supply electric vehicle manufacturer Tesla with a significant amount of lithium.

The product is a vital component used in lithium-ion batteries, including those found in electric vehicles.

In March, Core Lithium announced it had entered an arrangement with Tesla involving the potential supply of 110,000 tonnes of concentrate from its Finniss Lithium Project, 80 kilometres south of Darwin.

However, the deal was subject to a final agreement being reached by both parties by October 26.

But, in an announcement to the Australian Stock Exchange on Thursday morning, Core Lithium said the deal had not been completed by the due date.

"I want to thank Tesla for the time taken to negotiate with Core and look forward to maintaining an open and ongoing dialogue," Core Lithium chief executive Gareth Manderson said.

Despite the lack of an agreement with Tesla, the company said it remained "well positioned" to take advantage of strong global demand for lithium, following the official opening of the $89 million Finniss mine earlier this month.

Core Lithium said it had already sold 15,000 tonnes of direct shipping ore (DSO) to other buyers in the lithium-ion battery supply chain, which would be shipped by the end of the year.

It also said separate offtake contracts were already in place and amounted to 80 per cent of the Finniss mine's expected production over the next four years of its operations.

"The recent DSO sale, predicted commencement of lithium concentrate sales (next year) and an increasing lithium price environment indicate that Core Lithium is well positioned to capitalise on the high demand and current shortage of available battery grade lithium spodumene concentrate," Mr Manderson said.