ISTANBUL -- The blossoming trade relationship will be the focus of a one-day trip to Turkey by Russian President Vladimir Putin, though differences between the two countries over the conflict in Syria will likely be aired.
Putin's visit to Istanbul on Monday is his first trip in two months. The unusual break in his travel schedule fed speculation that the 60-year-old Russian leader is suffering from serious back trouble or another illness. His spokesman has attributed Putin's discomfort to a pulled muscle, and the president has appeared more mobile in recent days.
During the talks, Turkey is likely to argue for tougher action against Syrian President Bashar Assad. The Kremlin has shown no inclination of relinquishing its support for its last Middle East ally, whom it has shielded from international sanctions and continued to provide with weapons during an escalating civil war.
Russia and China have used their veto power at the U.N. Security Council to block any U.N. sanctions on Assad's regime over its crackdown on an uprising that began in March 2011. Advocates say at least 40,000 Syrians have been killed in the fighting since then.
Moscow has also insisted that it would honor weapons contracts signed earlier with Syria for the delivery of anti-ship and air-defense missiles. Despite Western demands to halt the trade, the Kremlin has argued that the sales don't violate any international agreements.
Russia and Turkey were recently at loggerheads over Syria.
In October, Russia reacted angrily to Turkey's decision to force a Syria-bound passenger plane flying from Moscow to land in Turkey because Turkish officials said there was military equipment on board. Moscow said the plane was legally carrying radar parts for Syria.
Yuri Ushakov, Putin's foreign affairs adviser, has said the incident may come up during Putin's talks with Turkish Prime Minister Recep Tayyip Erdogan. However, he signaled that Russia was not going to press its argument, saying the cargo, which has remained in Turkish hands, belongs to Syria.
And while Russia has voiced concern about the planned deployment of NATO's Patriot air-defense missiles on Turkey's border with Syria, it has carefully balanced its statements on the subject and avoided any sharp criticism of Turkey itself.
Ushakov said a candid exchange of views with Turkey will help "if not narrow the gap, at least understand each other's moves better."
Despite their apparent disagreements over Syria, Russia and Turkey have robust economic ties, which will be the main focus of Monday's talks. Turkey is a top consumer of Russian natural gas, while Russia is a major market for Turkish construction companies. Ushakov said trade between the two countries, which totaled $32 billion last year, is expected to grow to $100 billion in the coming years.
Among other projects, Russia is building Turkey's first nuclear power plant. Turkey is also a top travel destination for Russians, with more than 3.5 million Russian tourists visiting last year.
Putin had been expected to visit Turkey in October, but he postponed that and several other foreign trips, and instead spent most of the past two months at his suburban residence.
Various explanations have been put forward for Putin's discomfort, which first appeared at a summit of Asia-Pacific leaders in Vladivostok in early September.
The business daily Vedomosti claimed Putin had injured his back shortly before the summit in a widely publicized flight in a motorized hang glider.
However, Putin's spokesman, Dmitry Peskov, has portrayed Putin as a robust athlete who pulled a muscle during judo training, while his chief of staff, Sergei Ivanov, said Putin had sustained a "light sports injury."
Putin has not traveled by air since two brief trips in early October, one to Ulyanovsk, a city 725 kilometers (450 miles) from Moscow, and the second the next day to Tajikistan, a former Soviet republic in Central Asia.
Putin plans to visit Turkmenistan on Wednesday and make other foreign trips before the end of the year.