Mobile and especially efficient: Russia's S-300 anti-aircraft missiles can be used against fighter jets, cruise missiles and ballistic missiles. It's precisely these weapons that Syria wants to get its hands on, as soon as possible.

Ahead of his two-day visit to Russia, which begins Wednesday, Syrian Foreign Minister Walid al-Moallem (above, left with Russian Foreign Minister Sergei Lavrov) was clear. "We have told Russia that we want quality weapons," he said in an interview with a Lebanese newspaper - S-300 missiles, but also other weapons, he specified.

Russia has supplied Syria with weapons since Soviet times. In 2013, the Stockholm International Peace Research Institute (SIPRI) named Russia as Syria 's most important supplier, providing Damascus with about half of its weapons. In recent years, those numbers have been on a steady increase.

The especially lucrative transaction for Russia's S-300 anti-aircraft missiles was signed in 2010, just before the start of the ongoing civil war. In total, Syria is to be supplied with multiple rocket launchers and truck-based radar systems, according to Russian media reports. Details have been kept confidential.

Some media reports have claimed that the air defense systems, along with Russian military advisers, have already arrived in Syria. Russian President Vladimir Putin has so far only confirmed that a "single component" has been delivered.

'We must prepare ourselves'

In September 2013, Putin said in an interview that Russia has put further deliveries of the S-300 systems to Syria on hold. Now, however, it seems Syria wants to convince its trading partner to get things started once again.

Since September, US forces have been conducting airstrikes against the terrorist militia "Islamic State" (IS) in Syria. The government in Damascus, however, believes that its army is also in danger. "We must prepare ourselves," said al-Moallem before his Russia trip. "We don't know how [US President] Barack Obama will behave."

Just a few days ago, a spokesman for Russia's Foreign Ministry refuted claims that Russia's relationship with Syria had cooled. Russia has described S-300 systems as "defensive weapons," meaning these are not prohibited by international sanctions against Syria. And yet, experts like Dmitri Trenin of the Carnegie Moscow Center don't believe that Russia will now engage with Syria.

"Russia understands the consequences of delivering such supplies, considering what would happen if the S-300 systems fell into the hands of IS fighters," said Trenin, speaking with DW. However, Russia's reluctance could change if the US decides to attack Damascus and the Syrian army.

Financial support

Syria's foreign minister will likely bring up a second pressing issue during his visit: money. Syria wants to ask Russia for a loan of $1 billion (800 million euros) to stabilize its devalued currency, Russian media reported in late October. But Russia is not ready for such a loan, said a government source in the daily Kommersant newspaper.

The Syrian government has denied having asked Moscow for the loan. What's clear, however, is that Russia promised Damascus financial support in the amount of roughly 240 million euros in May. According to Russian media reports, a Russian bank has already paid out some 46 million euros to the Syrian government.

"Moscow is now closely watching its own financial resources," said Trenin. The Russian economy is currently facing "increasing difficulties," and there have been "new expenditures" in the form of the annexed Crimean peninsula and the mining region in the Donbass in eastern Ukraine, controlled by pro-Russian separatists.

Diplomatic backing

Since the start of the Syrian conflict between the government and rebel forces, Moscow has primarily offered diplomatic support. With its veto in the UN Security Council, Russia has put a stop to several resolutions against Syria. In addition, Moscow has also sent warships into the Mediterranean off the Syrian coast.

In the fall of 2013 President Putin was also able to head off an impending military strike by the US when he convinced Syrian President Bashar al-Assad to destroy his chemical weapons under international supervision, a development praised by both Moscow and Washington. But differences remain, with the US continuing to demand regime change in Syria as Russia continues to back Assad.

But Trenin believes that the rise of the IS terrorist militias in Syria and Iraq have brought Russia and the US closer together in recent months. "IS is a common enemy for Russia and the US," he said, pointing out that there are about 800 IS fighters who have come out of Russia.

Trenin, therefore, believes there's still a chance for a new international peace conference to resolve the conflict in Syria. In a statement on Tuesday, the Foreign Ministry in Moscow said that Russia was still willing to allow representatives of the Syrian government and the opposition to hold negotiations in Moscow.