Speaking to reporters before leaving for G-20 summit in Argentina on Thursday, Erdogan said the final currency composition had yet to be agreed but confirmed he expected the deliveries of the systems to take place in 2019, presstv.ir reported.
On Wednesday, Russian President Vladimir Putin said it is impossible to seal the S-400 agreement with Turkey in dollar.
The Russian president said he and Erdogan had agreed on another option.
Putin also criticized the US administration for using the dollar as a pressure tool, stating that Russia and its trade partners are working to create interbank payment systems independent of the Belgian-based SWIFT global payment network.
A number of the US-led North Atlantic Treaty Organization (NATO) member states have criticized Turkey for its planned purchase of S-400 missile defense systems from Russia, stating that the move could jeopardize Ankara's acquisition of F-35 fighter jets.
On July 15, the top American Air Force general in Europe warned that the Turkish government’s plan to purchase Russian S-400 systems would give the advanced air defense shield deep insight into the US radar-evading F-35 fighter jets.
Erdogan has emphasized that Ankara would utilize sophisticated S-400 anti-aircraft missile systems if necessary.
Erdogan and his Russian counterpart said in the Turkish capital Ankara on April 3 that they had agreed to expedite the delivery of S-400 missile systems. The delivery is expected to start between late 2019 and early 2020.
Turkey’s English-language Hurriyet Daily News newspaper reported on December 29 last year that the loan deal for four S-400 surface-to-air missile batteries had been signed in Ankara.
The developments came only two days after Chief Executive Officer of Russian state corporation Rostec Sergey Viktorovich Chemezov told the Kommersant daily newspaper that Russia would supply Turkey with four batteries of S-400, worth $2.5 billion each, and Moscow was expected to begin the first deliveries in March 2020.
Chemezov added that Turkey would pay 45 percent of the cost of the agreement up front, while Russia would provide loans to cover the remaining 55 percent.
The S-400 system, whose full name is the Triumf Mobile Multiple Anti-Aircraft Missile System (AAMS), is an advanced Russian missile system designed to detect, track, and destroy planes, drones, or missiles as far as 402 kilometers away. It has previously been sold only to China and India.
Turkey is striving to boost its air defense, particularly after Washington decided in 2015 to withdraw its Patriot surface-to-air missile system from Turkey's border with Syria, a move that weakened Turkey’s air defense.
Before gravitating towards Russia, the Turkish military reportedly walked out of a $3.4 billion contract for a similar Chinese system. The withdrawal took place under purported pressure from Washington.
Ankara’s ties with its Western allies in NATO have been strained over a range of issues.
Erdogan has been critical of Washington for supporting Kurdish groups in Syria that he says are responsible for terror attacks inside Turkey.
The Turkish leader has also slammed American officials for rejecting his requests to hand over Fethullah Gulen, a powerful opposition figure living in the US, whom Ankara accuses of having masterminded the July 2016 coup attempt.