LONDON, April 23 (Reuters) - The London Metal Exchange (LME) moved on Tuesday to stop traders from taking Russian aluminium from its approved warehouses and returning it at a later date to profit from rule changes to comply with new sanctions.

The U.S. and Britain earlier this month banned the LME from accepting new Russian production of aluminium, copper and nickel to restrict Russian revenues from the export of these metals.

The London exchange has banned from its system Russian aluminium, copper and nickel produced from April 13 to comply with the sanctions imposed over Russia's invasion of Ukraine.

For metal produced before April 13, LME rules differentiate between Type 1 and Type 2 Russian warrants which created an opportunity to tie up metal in lucrative "rent deals". Warrants are title documents conferring ownership.

Type 1 contracts allow UK LME members and their clients to freely trade Russian metal warrants in existence before April 13. Type 2 covers Russian metal produced before April 13 but not yet on LME warrant, and which UK companies can only trade or take physical delivery of for non-UK clients.

"When a Type 1 Russian Warrant is re-issued, the owner has the option to convert it to a Type 2 Russian Warrant," the LME said in a release to its members.

"However, this does not change the fact that ... the warrant may still be cancelled (metal earmarked to leave LME warehouses) and loaded-out by UK Persons because it was on warrant as at the end of 12 April 2024."

Metal industry sources said clarification of the rules was to stop rent deals or agreements that allow LME warehouses to share their fees or rental income with companies that deliver metal to them.

Under rent deals, the company that delivers metal to a warehouse does not have to retain ownership, but can get a share of the rent, paid by the new owners, for as long as the metal stays in that warehouse.

"The LME has made some refinements to its approach, with the aim of ensuring fairness, reducing administrative burden and facilitating the circulation of globally usable metal without compromising the protection of its market from potential breaches of UK sanctions," the exchange said in response to a request for comment. (Reporting by Pratima Desai; Editing by Marguerita Choy)