The German chancellor will visit the Oval Office for a tete-a-tete as divisions grow over how to stop bloody fighting between Kiev and Russian-backed rebels.
US President Barack Obama hosts Angela Merkel at the White House on Monday, as worsening violence in Ukraine confronts them with a choice between throwing more weapons into the war and risky peace talks.
At home Obama is facing increasing calls to supply the outmatched Ukrainian army with more weapons to shore up its faltering defenses.
Merkel and many European nations believe weapons could not overturn the military mismatch between Ukraine and the might of the Russian army and would simply escalate a conflict that has left 5,400 people dead in less than a year.
Merkel has instead sought to negotiate a peace deal with Russian President Vladimir Putin, jetting in to Moscow last week with French President Francois Hollande for crisis talks.
A summit of leaders of Ukraine, Germany, France and Russia is tentatively planned for later this week, after Merkel leaves Washington.
She is likely to leave the US capital with Obama's tone of skepticism ringing in her ears.
Many in the Obama administration believe that Putin will use the talks as a stalling tactic, after failing to live up to a previous peace deal agreed in the Belarusian capital Minsk in September.
US Vice President Joe Biden gave a hint of the White House's stance on a recent visit to Germany.
"Given Russia's recent history, we need to judge its deeds not its words. Don't tell us, show us, President Putin," Biden told a global security conference in Munich.
"Too many times president Putin has promised peace and delivered tanks and troops and weapons."
While he did not directly say that Washington would provide arms to Kiev, Biden insisted Ukraine had the right to defend itself from pro-Russian separatists.
Any decision to arm the Ukrainians is likely to come after it becomes clear talks are not working.
Washington has also indicated that further sanctions against Russia could be on the way.
But there too the United States seems at odds with its European allies, with Washington looking for more robust measures.
European foreign ministers recently agreed to extend existing sanctions and increase the number of people on the sanctions list by 19, modest measures that are unlikely to alter Putin's calculus.
But the White House is keen to play down talk of a split, which is certain to be exploited by Putin.
"The president values the chancellor's judgement and appreciates her strong efforts in marshalling European support and maintaining transatlantic unity throughout the Ukraine crisis," a senior administration official told AFP.
"She has been tireless in her pursuit of a diplomatic solution to the crisis and the president anticipates a useful and informative discussion about this and other issues."
By Andrew Beatty (AFP)