The warning came days after the US vice-president, Joe Biden, said Washington would be prepared for direct talks with Iran if Khamenei showed seriousness.
And to show seriousness of intent, after this month's European election the EU could also fill a big position in Brussels with a robust and competent east European (perhaps Mr Sikorski himself).
Ben Rhodes, the deputy White House national security adviser, said on Air Force One that Washington wanted a "positive environment" in the talks with Tehran showing "seriousness" about moving forward with dialogue, news agencies reported.
Khar, who said she was "exasperated and discouraged" by the failure of the Chequers summit, said Afghanistan's leaders had been guilty of "playing to the public gallery" and not showing "seriousness of purpose and approach".
Aides drew comparisons, as incoming administrations often do, to the frenetic activity of Franklin Roosevelt's early months in office, during which he signed 15 big bills.Michael Leavitt, the former Utah governor who chaired Mr Romney's transition team, describes plans to deliver a "jolt of confidence" by showing seriousness in a few big areas.
Both show seriousness and commitment to the field that can often be lacking in scientists unsure of what they want to do away from the bench.
Nothing like a face-to-face meeting to show seriousness of intent.
The former will be cast as pro-jobs; the latter will be cast as showing seriousness about the nation's long-term budget problems.
To show seriousness, Wall Street should cancel fundraisers for the RNC and Congressional and Senatorial campaign committees unless and until they behave.
Well, it shows seriousness in a conflict, classifies the enemy, justifies spending and empowers political and legal correctness for global multilateral mobilization.
