Iron ore pricing has caused tension between buyers and sellers
Two of the world's biggest mining companies have agreed landmark deals with Asian steel mills to buy iron ore on quarterly contracts.
The deals could mark the end of annual contracts that have formed the basis for pricing in the steel industry for decades.
Vale and BHP Billiton said the new system was fairer and more transparent.
The price of iron ore under their first quarterly contracts has risen strongly, reflecting increased demand.
According to reports, Brazil's Vale is now charging Japan's Nippon Steel around $105 per tonne of iron ore.
By Will Smale, BBC News business reporter
BHP and Vale's announcements could mark the end of an era.
For decades global iron ore prices have been set on an annual basis, the idea being that 12-month pricing brings much-needed stability to what has always been a volatile industry.
However, the big growth in iron ore also traded freely on the markets - so called 'spot' iron ore - has put increasing pressure on the annual price arrangement in recent years.
Four years ago, only 4% of iron ore was available to buy on the spot market, but this has now risen to about one third - with most being bought by China.
When the spot price has been significantly below the set annual price, the steelmakers complain, and when it is above, it is the iron ore firms that are unhappy.
By switching to quarterly pricing, BHP and Vale hope that the fixed price will more closely mirror that of the spot market, and be more able to respond to changes in iron ore demand.
It remains to be seen whether Rio Tinto - the third of the big three iron firms will follow BHP and Vale's lead.
And more importantly, whether China - the world's largest importer of iron ore - will also agree to accept quarterly pricing.
In recent years China has strongly opposed the annual prices the iron ore firms have offered - saying they are too high - but continued to support 12-month pricing in principle.
This compares with the 2009/10 annual price of around $62, that expires on Wednesday.
If Vale and Anglo-Australian BHP had continued with annual pricing, it is likely that the new annual price would also have been set around $105 per tonne, as demand for iron ore is now rising strongly again compared with 2009's much lower volumes.
But by moving to quarterly contracts, the two firms are hoping to end the friction that the old annual pricing system caused, especially when the cost of iron ore on the open market moved strongly up or down away from the fixed 12-month price.
"BHP Billiton today announced that it had reached agreement with a significant number of customers throughout Asia to move existing iron ore contracts that were previously priced annually onto a shorter-term basis," said BHP.
Pedro Gutemburg at Vale said: "The old system generates never-ending confrontations between buyers and sellers."
While Vale said it had signed new quarterly agreements with Japanese and South Korean steelmakers, BHP was more vague, only saying it had reached agreement with "a significant number of customers throughout Asia".
This leaves open the question as to whether China - the world's largest importer of iron ore - has also agreed to the new quarterly deals.
Some analysts have speculated that some smaller Chinese steel firms have also signed up, but the Chinese government has yet to make any announcement.
It also remains to be seen whether Rio Tinto, the third of the big three iron ore companies will follow Vale and BHP's lead. It has not yet commented.
Iron ore negotiations is a sensitive subject for Rio, especially a day after four of its executives were jailed in China for bribery related to iron ore price talks.
Some analysts think Rio will ultimately follow suit.
"Annual prices are a relic of the past," said Tim Schroeders at Pengana Capital.
"In today's environment, you need to be able to adjust to the market reality a lot quicker than on an annual basis."