In her news conference, she also highlighted the importance of a close trans-Atlantic relationship with the U.S. despite current differences in opinion with Trump in some areas.
Last week, Trump said Germany was wrong to allow a new $11-billion Baltic Sea pipeline to import even more Russian gas, while being slow to meet targets for North Atlantic Treaty Organisation spending.
Merkel made the statement in a wide-ranging news conference on July 20 after U.S. President Donald Trump accused Berlin last week of being a "captive" of Russia due to its reliance on Russian energy imports.
The president's trip to NATO last week began on a tough note when he started the meeting by unleashing his fury on NATO Secretary General Jens Stoltenberg for defending Germany's energy partnership with Russian Federation and threatened Berlin with US action over the deal that he said was wholly inappropriate.
The German chancellor vowed to keep lobbying Mr Trump to head off trade tariffs, which could escalate a trade war and threaten the global economy.
Merkel said she believed the debate over migration policy was an important one to have, but that the tone of the discussion "was often very harsh, and I attach a very, very great importance to the language".
Trump has come under fire following the Helsinki talks for what many saw as his unsettling embrace of the Russian strongman, as well as his seeming disavowal of his own intelligence agencies and their assessment that Moscow meddled in the 2016 election.
"I find that meetings between the USA and Russian presidents must return to normality", she added.
Archaeologists have discovered the remains of the world's oldest snakes
The experts also examined a second piece of amber containing what appears to be a fragment of skin from an adult snake. The skeleton of the snake, which is under five centimeters in length, is relatively complete, aside from the skull.
"We can't rely on the superpower of the United States", Merkel told a news conference in Berlin, Reuters reports.
Asked if she was exhausted, Merkel, who has been in office since 2005, replied: "I can't complain".
She also expressed hope that a trade war with the United States could be staved off, ahead of European Commission chief Jean-Claude Juncker's visit to Washington next week to try and negotiate a solution.
But she also warned that Washington could no longer be relied on to deliver world order.
Despite trade and spending disputes between the USA and Germany, Merkel stressed the importance of maintaining a good relationship.
'We see these potential tariffs both as a breach of WTO rules and also as a danger to the prosperity of many in the world, ' she said.
"On the issue of trade, we have a very serious situation in the world, I want to make that very clear", Mrs Merkel said.