LONDON (Reuters) – British Foreign Secretary David Cameron used a visit to Washington on Thursday to urge politicians in the United States to approve a fresh package of military aid for Ukraine. U.S. President Joe Biden has pleaded with Republicans for a fresh infusion of military aid for Ukraine, warning that a victory for Russia over Kyiv would leave Moscow in position to attack NATO allies and could draw U.S. troops into a war. However, Senate Republicans on Wednesday blocked Democratic-backed legislation that would have provided billions of dollars in new security assistance for Ukraine, s…