WASHINGTON (Reuters) - Secretary of State Hillary Clinton told Myanmar's foreign minister and pro-democracy leader Aung San Suu Kyi in a call on Saturday the United States is "committed to walking down the path of reform" with the Southeast Asian nation.

One day after President Barack Obama's administration said it would upgrade ties with Myanmar in response to its amnesty for hundreds of political prisoners and other reforms, Clinton told Foreign Minister Wunna Maung Lwin Washington is prepared to meet action with action.

But she said it was important Burma take steps to unconditionally release all remaining political prisoners, end violence and human rights abuses in ethnic areas and address concerns about the country's military ties to North Korea.

Details of Clinton's phone call were outlined in an emailed statement from State Department spokeswoman Victoria Nuland.

Clinton and Suu Kyi exchanged views on by-elections set for April 1, and the need to continue to work for national reconciliation. Suu Kyi said she supports U.S. efforts to engage the government in Yangon.

Myanmar held elections last March that saw a nominally civilian government - although still heavily weighted toward the military - take over from the ruling junta and launch what has become a rapid series of political reforms.

Those have included freeing Suu Kyi in November 2010, loosening media restrictions and other repressive laws, and working to end long-running conflicts with ethnic insurgent groups, including Karen rebels who signed a ceasefire on Thursday.

Clinton's trip to the isolated nation in December ended some five decades of official estrangement. At the time, she promised the United States would respond to further reforms.

(Reporting By Deborah Zabarenko; editing by Todd Eastham)