US diplomats' Syria memo is important statement: John Kerry

US Secretary of State John Kerry said on Friday that an internal memo on Syria signed by more than 50 US diplomats is an "important statement" that he would discuss when he gets back to Washington.

The memo is sharply critical of US policy in Syria, calling for military strikes against President Bashar al-Assad's government to stop its persistent violations of a civil war ceasefire.

"It's an important statement and I respect the process, very, very much. I will ... have a chance to meet with people when I get back," Kerry said during a visit in Copenhagen. He said he had not seen the memo.