"This additional support highlights the partnership between the United States and the Syrian people in ending the humanitarian disaster and putting Syria on the path to genuine democratic transition," the bloc's US representative, Najib Ghadbian, said in a statement.
The National Coalition, which described itself as the best alternative to the Assad regime, added in the statement that it "appreciates American support to the Syrian people in their struggle".
In a keynote speech to the West Point military academy on Wednesday, Obama vowed to increase US support for the rebels fighting Assad's regime and to help them confront their extremist rivals.
"I will work with Congress to ramp up support for those in the Syrian opposition who offer the best alternative to terrorists and a brutal dictator," said Obama.
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The announcement comes two weeks after the US president met with the head of the National Coalition, Ahmad Jarba.
Officially, US support for rebel fighters in Syria has been limited to non-lethal aid amounting to $287 million, though the CIA reportedly participates in a secret programme to train moderate rebels in Jordan.
Opposition leaders are particularly dismayed that the United States has balked at providing anti-aircraft missiles to rebels, fearing they could fall into the wrong hands.
The Wall Street Journal reported Tuesday that Obama was ready to sign off on training missions for selected rebel groups, to counter the rising power of Al-Qaeda-linked extremists.