Heavy US equipment that arrived in Germany on Sunday is bound for Bulgaria, a specialized website has said.

The Abrams main battle tanks, three howitzer artillery cannons and six light armored reconnaissance vehicles were first transported to Bremerhaven, Germany, and are accompanied by 160 Marines, according to the Marine Times.

The unit that is due to be deployed and based at the Novo Selo training area (near Sliven, Southeastern Bulgaria) will be part of the Black Sea Rotational Force, a semi-annual rotation of Marines and sailors.

Lt Col John Sattely, director of logistics for US Marine Corps Forces Europe and Africa, is quoted by Military.com as saying that the transportation of a Marine Corps combined arms capability in the Black Sea region "has fostered improved communication and coordination with the allied force and its partners".

"From the Bulgarians point of view, having the American flag flying there is proof to anyone that the U.S. is committed to the region," Luke Coffey, a former Army captain and now a fellow at Washington think-tank the Heritage Foundation, is quoted by the Marine Corps Times as saying.

In September, an exercise called Operation Brave Warrior will demonstrate mobility from Germany across the Danube river into Hungary.

Though not explicitly designed to send any signals to Russia in light of tensions over the developments in Ukraine, Us actions are aimed at demonstrating "US mobility and resolve with its allies," according to army official.

Last year NATO decided to step up defences at its eastern flank to be able to withstand what it perceives as "potential aggression" from Russia.   

In June, reports that the Pentagon was intending to deploy heavy equipment in the Baltics and Eastern Europe sparked controversy in Bulgaria, with the government sending mixed signals to the public as to whether the step had been coordinated with US allies.