UPDATE: Trump, Merkel Share Concerns Over Syria as Russia Continues Largest Naval Build Up Since War Began

The Russian Ministry of Defence said on Monday it had noticed Washington was building up its military forces in the Middle East in preparation for what Moscow feared was a possible strike on Syrian government forces, Russian news agencies reported.

Major-General Igor Konashenkov was quoted by agencies as saying that the USS Ross, a guided-missile destroyer, had entered the Mediterranean on Aug. 25 armed with 28 Tomahawk cruise missiles capable of hitting any target in Syria.

Read more: Iran and Syria Seal Military Cooperation Agreement

Up to 13 Russian warships have crossed the Bosphorus toward Syria so far this week as tensions between the U.S. and Syria continue to rise, according to ship spotters based in the Bosphorus Strait.

The deployment of the Russian fleet comes as the U.S. President Donald Trump threatened to strike the Syrian Army ahead of the long-awaited battle of Idlib. Syria, Turkey, Russia and U.S. are about to square off in the northern Syria city with millions of civilians in the crosshairs

Turkey's foreign minister said last Friday it would be disastrous to seek a military solution in the Idlib region, a rebel-held enclave which the Syrian government says it aims to recapture.

Idlib is a refuge for civilians and rebels displaced from other areas of Syria as well as for powerful jihadist forces. It has been hit by a wave of air strikes and shelling this month in a possible prelude to a full-scale government offensive.

Turkey has backed some rebel groups in the region and set up a dozen military observation posts. It is trying to avert an attack by forces loyal to Syrian President Bashar al-Assad, who is backed by Moscow.