MUNICH (Reuters) - The United States and Russia formally inaugurated their new START nuclear arms treaty on Saturday, capping two years of work to "reset" the sometimes strained ties between the former Cold War enemies. US Secretary of State Hillary Clinton and Russian Foreign Minister Sergei Lavrov exchanged the final START documents at the Munich security conference, where two years ago US Vice President Joe Biden launched the Obama administration's push for better relations with Moscow. "Two years ago we all laughed about the translation of the ceremonial 'reset' button I gave to the Foreign Minister," Clinton said, referring to a diplomatic gaffe in which she presented Lavrov with an oversized button on which "reset" was mistranslated into the Russian for "overcharge."