"I have seen some stupid things from that government," said Sen Patrick Leahy, who co-sponsored the amendment. "I have seen some things that make you wonder what universe they live in. But this one just went beyond the pale."
Republican Sen Lindsey Graham agreed, calling talk of an exit tax on US property "ridiculous" after a dozen years of American-led stabilization efforts in Afghanistan.
The levies were described in a June 28 letter to lawmakers identifying almost USD 1 billion in business taxes and penalties imposed by the Afghan government on contractors supporting US operations.
The US special investigator for Afghanistan warned of hundreds of millions of dollars in additional future costs if Congress doesn't act.
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Since 2002, Congress has spent more than USD 90 billion on humanitarian and reconstruction programs in Afghanistan.
That doesn't include hundreds of billions of dollars more in military costs.
The bill slashes the State Department's diplomacy and aid budget by 5 per cent from last year, but is far less severe than the 20 per cent reduction approved by a House panel last week.
Like the House, the Senate provides full funding for embassy security to guard against any repeat of last year's deadly attack in Benghazi, Libya.
However, the Senate maintains payments for several UN agencies that the House wants to cut funding for completely.
The Senate's bill proposes spending of USD 50.6 billion.