ISTANBUL (Yonhap News) -- South Korean President Lee Myung-bak called Saturday for closer economic ties with Turkey befitting the "brotherhood" relationship between the wartime allies, saying a free trade deal would be a good way to lift economic relations.

Lee made the remark during a meeting with Turkish and South Korean business CEOs after arriving in the ancient city of Istanbul for a four-day visit focused on bolstering economic cooperation and upgrading the traditional friendship between the two countries.

During the 1950-53 Korean War, Turkey sent the fourth-largest number of troops after the United States, Britain and Canada to help South Korea repel communist troops from North Korea. The two countries call each other "brother countries" due to the strong bond forged in blood.

"The peoples of the two countries consider each other a brother nation, but economic relations of the two countries are not balanced with those of brother countries," Lee said. "I think an FTA would serve as a new opportunity to develop efforts to facilitate" economic relations.

South Korea and Turkey have held three round of negotiations on forging a free trade agreement since the first round in April 2010.

Lee said that a breakthrough can be made in the negotiations if both governments make joint efforts through summit talks.

Lee later attended a dinner reception hosted by Istanbul Governor Huseyin Avni Mutlu.

On Sunday, Lee is scheduled to meet with Prime Minister Recep Tayyip Erdogan before heading to Ankara for summit talks with President Gul. Key topics of the summit, set for Monday, include trade expansion, infrastructure construction and other issues of cooperation.

The two sides are also expected to agree on upgrading their ties to "strategic partnership."

The trip to Turkey is part of a four-nation tour that will take him to three major oil producing nations -- Saudi Arabia, Qatar and the United Arab Emirates. The countries account for about half of South Korea's crude imports.

The swing through the Middle East comes as South Korea prepares to cut back on its crude imports from Iran in line with a U.S.-led campaign to dry up the country's oil export revenues as punishment and pressure over its nuclear weapons programs.

Iranian crude accounts for some 10 percent of South Korea's total oil imports. Concerns have arisen that a drastic cut could have negative effects on Asia's fourth-largest economy. Officials said a key focus of Lee's trip will be to ensure there will be no disruptions to the oil supply after Seoul cuts back on Iranian imports.

Officials said they are optimistic about securing commitment from the three nations to increase their oil production to make up for the shortfall in South Korea's oil imports because the countries are also concerned about the prospect of a nuclear-armed Iran.