President Barack Obama signed an order authorising the US government to begin cutting $85 billion (£57bn) from federal accounts. By so doing he officially enacted across-the-board reductions that he was opposed but failed to avoid.
Obama acted as the deadline for the president and Congress to avoid the steep, one-year cuts approached on Friday night in the US.
Obama insisted on replacing the cuts, known as a "sequester" in government budget language, with tax increases and cuts spread out over time. Republicans rejected any plan that included tax revenue.
The government said reductions will soon result in furlough notices to government employees and will trim government spending on defence contracts and in domestic government programs. Active military personnel and anti-poverty and low-income assistance programs are largely protected from the cuts.