WASHINGTON (Reuters) - President Barack Obama on Tuesday asked Congress to avoid deep spending cuts with a stopgap bill and said he is committed to cutting the nation's deficit to manageable levels over the long term.

Obama said uncertainty over the automatic across-the-board cuts - known as sequestration - has stunted economic growth and has the potential to do further damage.

A round of deep cuts would kick in March 1 unless Congress acts, and the president asked lawmakers to pass a modest bill that would blunt the impact of the reductions for several months to allow time to produce a broader package to address the deficit.

Obama said he remains committed to achieve the full $4 trillion in deficit reduction seen as necessary to bring the nation's sea of red ink under control. But he insisted that deficit reduction come in part from tax reforms.

(Reporting By Mark Felsenthal; Editing by Sandra Maler)