ANKARA, Turkey — Tusas Turkish Aerospace Industries (TAI) is negotiating with Pakistan to upgrade 74 Pakistani Air Force (PAF) F-16 fighters, company officials said.

"The negotiations are being held through our Pakistani representative," a TAI official said. "We are hopeful about an eventual deal in view of our excellent relations with PAF."

If finalized the deal will involve upgrades on a batch of 74 PAF F-16 aircraft, including 14 fighters Pakistan will acquire from Jordan.

But for any Turkish-Pakistani deal a US go-ahead is required.

"We are in talks [with the Pakistani officials] but it is not certain that we shall win the contract," the TAI official said. "These [Pakistani] aircraft will need a US permission for any upgrade program."

In an earlier upgrade program for 41 F-16s, Pakistan wanted the job to be done locally but failed to win US permission. But the US agreed that TAI could carry out the upgrade work.

In September 2014, TAI delivered the last batch of four upgraded F-16s to PAF. That program involved avionics and structural modernization.

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TAI, which assembled F-16 fighter jets in Turkey in the 1980s and 1990s, today manufactures parts for Boeing helicopter-maker Sikorsky. The company also is a participant in the multinational Joint Strike Fighter program and the A400M, known in Turkey as the Future Large Aircraft.

TAI has upgraded scores of Turkish F-16s, too. But in a more ambitious program the company has been designing an indigenous Turkish fighter aircraft.

"Pakistan wants the new upgrade program to be done locally, like in the first program," said a Turkish procurement official. "Local upgrade work is their first choice but if they fail to win the US permission for that they will probably go for the TAI option, like in the previous deal."

A team of TAI and Turkish procurement officials will visit Pakistan in July for detailed talks on the F-16 upgrade program.

A Turkish official said that Ankara expects contract negotiations with Pakistan, including potential US approval for TAI's upgrade deal, would take around two years.

"There is a lot to discuss, negotiate and discuss and negotiate again," said one procurement official familiar with the contract.

He said that at this stage it is not clear what the Pakistani upgrade program will involve.

"The [Pakistani] requirement is not clear in terms of technological concept," the official said. "It is not clear at this stage what upgrades would be involved and how much the work will cost."

The previous TAI-PAF contract covering upgrades on 41 aircraft was worth $64.5 million. The 2008 deal saw TAI upgrade Pakistan's older and then-newly acquired surplus F-16s to Block-52+ standard from 2010 onward.

Industry sources say if the Pakistani requirement is similar to that in the previous contract the new deal could be around $100 million.

Turkey and Pakistan traditionally have had good political relations. In recent years Pakistan has become an emerging market for Turkey's defense companies, including a deal for the midlife upgrade of Pakistani F-16s, and Turkish engineering support for a logistical support ship for the Pakistani Navy.

A deal for a fleet tanker/replenishment ship was signed by Pakistan's Karachi Shipyard & Engineering Works and Turkish technology and engineering firm STM in 2014. The vessel will be built in Karachi under STM supervision and delivered in 2017.

But Turkish officials usually view Pakistan as "not rich enough in cash" to buy the equipment or work Turkish companies wish to sell. A large Turkish-Pakistani deal to help Pakistan build Turkish designed corvettes fizzled out in 2009 when Pakistan's economy tanked, and matters have hardly improved since then.