Poroshenko will meet with Obama and address Congress as he seeks military and economic assistance.
Lawmakers approved an association accord with the E.U. and granted more autonomy to eastern regions.
Poroshenko says the “fate of peace” hinges on rebel acceptance of political compromises.
Amb. John Tefft won’t use Twitter, a back-to-basics approach in the worst time for U.S.-Russia relations since the Cold War.
But Poroshenko still faces challenge to win support for the cease-fire deal with pro-Moscow rebels.
Firefights are reported near key eastern cities as the government tries to sell the peace plan to the public.
Artillery bombardments are heard near the key city of Mariupol.
The agreement sets up a familiar scenario for Russian control over another ex-Soviet Union satellite.
People interviewed in both Kiev and the east are weary of war but still deeply divided on a way forward.
The plan would entrench gains by Russian-backed rebels, which could be difficult for Ukraine to accept.