April 18 (Bloomberg) -- The cost of shipping commodities by sea may climb as an increasing number of vessels are sailing to Brazil's two largest iron ore ports, cutting supply elsewhere, Sempra Metals said.

Ships with a carrying capacity of about 20.6 million metric tons are bound for Brazil's iron ore ports of Ponta da Madeira and Tubarao, a 25 percent increase since the end of February, Sempra Metals analyst John Kemp in London wrote in an e-mailed note today, citing data from Cia. Vale do Rio Doce.

``The shipping market appears to have tightened back to levels last seen in November 2007'' when rates climbed to a record, he said. Ship queues at Australia's Newcastle, the world's largest export harbor for coal, remain similar to last year, further tying up vessels, he said.

The cost of shipping commodities to China from Brazil, at $73 per ton, is 19 percent below the $90 a ton record it set last year, Kemp wrote.

To contact the reporter on this story: Alaric Nightingale in London at Anightingal1@bloomberg.net

Last Updated: April 18, 2008 07:37 EDT