Ukraine has raised the alarm over an increase in Russian forces near its eastern border as violence has risen along the line of contact separating its troops from Russia-backed separatists in its Donbass region.
"The Chancellor demanded that this build-up be unwound in order to de-escalate the situation," Germany's government said in a readout of a telephone call between Merkel and Putin.
The legislation, which could pave the way for Putin to stay in power until 2036 should he choose to do so and win re-election, reflects sweeping changes to the constitution that were brought in last year.