伊朗外交部长：华盛顿不断变换立场延长了核谈判的时间。

Group 1 - The core viewpoint of the article is that the Iranian Foreign Minister claims that Washington's constantly changing positions have prolonged the nuclear negotiations [1] Group 2 - The article highlights the impact of U.S. policy shifts on the timeline of nuclear talks, suggesting that these changes create uncertainty and hinder progress [1]