(Adds economist comment, details on borrowing)
ABUJA, Nov 7 (Reuters) - Nigerian President Muhammadu Buhari presented a record 8.6 trillion naira ($28.16 billion) budget for 2018 on Tuesday to foster shaky growth in Africa's largest economy as it emerges from its first recession in 25 years.
This is Buhari's third budget to parliament and like the previous ones, sets a record high level of spending, but analysts say implementation, particularly on capital expenditure that is meant to drive infrastructure development, has been lacking.
"Mostly, I think that they are setting themselves yet more unattainable goals," said John Ashbourne, Africa economist at Capital Economics.
"The federal government falls short on its revenue and expenditure targets every year, and Buhari always responds by writing an even more ambitious target into the budget for the following year," he said.
With 2.4 trillion naira of intended capital spending, the budget forecast a deficit of 2.005 trillion naira ($6.56 billion), down from last year's 2.36 trillion naira.
To help plug that gap, Buhari said the government would borrow 1.699 trillion naira, half of it from overseas.
Debt costs are, however, already high in Nigeria and the president also said almost a quarter of the budget's expenditure would go to servicing debt.
Economists have also noted that while the budgets reach new highs, they have risen at a slower clip than inflation. The new budget is about 16 percent higher than the previous year's, while Buhari said inflation for 2018 is expected to be 12.4 percent.
He told parliament that the budget was based on an exchange rate of 305 naira to the dollar, and a projected oil output of 2.3 million barrels per day at an assumed price of $45 per barrel.
He said he was targeting Jan. 1, 2018 for passage of the new budget and that the deficit is expected to be 2.005 trillion naira, with real economic growth estimated at 3.5 percent for 2018.
But previous budgets have been beset by wrangling with lawmakers over line items. The 2017 budget was not signed into law until halfway through this year, and even then, some spending was still being debated.
The 2018 budget must still be approved by the lower and upper chambers of parliament before it can be signed into law, a process that can take many months. ($1 = 305.8000 naira) (Reporting by Paul Carsten, Libby George and Camillus Eboh in Abuja and Chijioke Ohuocha in Lagos; editing by Emelia Sithole-Matarise)