UPDATE 1-Switzerland, Germany to revise taxation treaty

* Swiss finance minister calls for equal treatment

* Urges improved tone for debate

* Negotiations could take some time

* OECD to discuss tax havens on Tuesday (Writes through; adds details, background)

By Jason Rhodes

ZURICH, June 22 (Reuters) - Switzerland and Germany have agreed to revise their double taxation agreement, the Swiss Department of Finance said on Monday, easing diplomatic tensions between the countries over Swiss bank secrecy.

"Due to the diverse economic ties between the two countries, negotiations to do with the new agreement will take some time," the department said in a statement.

The announcement came after a meeting in Berlin between Swiss Finance Minister Hans-Rudolf Merz and German counterpart Peer Steinbrueck ahead of a summit on Tuesday of ministers from OECD countries, where leaders are expected to pressure nations like Switzerland to step up efforts toward bank transparency .

A statement to be released following the Berlin meeting, jointly hosted by the German and French governments, will state whether countries on a "grey list" drawn up by the Organisation for Economic Co-operation and Development (OECD) have made progress since last year.