A US refiner put a tanker owned by Thenamaris on subjects at a firm price, sending spot rates for medium-range (MR) tankers higher to start the week.

The 46,000-dwt Seabright (built 2006), which is currently at anchorage in El Palito, was put on subjects for early April loading, according to brokers. The refiner is said to be offering World Scale (WS) 147.5 for the US Gulf-to-Europe voyage.

The Baltic Exchange's assessment for rates on the TC 14 backhaul firmed to WS 145, up from WS 140 on Friday.

The charterer is also said to be offering WS 240 on the US Gulf-to-Brazil voyage.

MR rates have been on a tear since last week, with the Baltic's MR Atlantic basin time-charter basket reaching a three month high of $21,499 per day, up from $12,856 a week earlier. MJLF says the rate spike follows the drop in prompt tonnage available in the US Gulf.

"The lack of tonnage ballasting from the Atlantic coast to the US Gulf has finally been felt in a much tighter position list."

Chartering managers say demand in other market such as the European continent and the Mediterranean remain strong. Vessels are also experiencing strong delays in West African ports, limiting vessel availability.

Charterers are also reletting MRs to taking advantage of better rates. The Alma Maritime-owned 50,500-dwt Box (built 2007) is said to be on relet to a trading firm for $775,000 lumpsum.

The strength in the Atlantic basket comes as US clean products inventories are down versus year ago levels, according to Wells Fargo. Owners have said such destocking will be necessary before clean tanker demand resumes growth.