Israeli Prime Minister Benjamin Netanyahu, under heavy fire at home over planned legal reforms, was due to arrive Wednesday in Berlin where Germany's leaders will also urge him to reconsider the overhauls.
The German government is under pressure for hosting Netanyahu at a time of the disputed reforms, with critics urging Berlin to scrap the visit.
Netanyahu, speaking before boarding his plane to Germany, said Iran would be the "main issue" of his discussions, along with "other topics important to Israel".
"The security issues don't pause, even for a moment," he added.
German President Frank-Walter Steinmeier, speaking in Tallinn on Wednesday, said he planned to raise the reforms with Netanyahu when they meet on Thursday.
Israel is the "only democracy in the whole region, a country with a strong constitutional state", he said.
"What I would like to see is that what we have admired about Israel... is preserved."
Netanyahu's government, which includes ultra-Orthodox and extreme-right parties, introduced its judicial reform package in January.
The changes would allow lawmakers to override Supreme Court decisions that strike down legislation with a parliamentary majority, and then deny the court the right to review such a move.
It would also make it harder for the Supreme Court to strike down legislation it deems to contravene Basic Laws, Israel's quasi constitution.
Netanyahu's government has argued the reforms are needed to limit judicial overreach, but protesters have decried them as threatening Israel's liberal democracy by weakening key checks and balances.
Ten consecutive weeks of nationwide demonstrations have followed, with critics also charging that the proposed changes aim to protect Netanyahu as he fights corruption charges in an ongoing court battle.
Ahead of Netanyahu's departure, critics took their protests to Ben Gurion airport.
"Dictator on the run" and "Don't come back", read placards held up by demonstrators near the airport, where a convoy of cars bearing Israeli flags circulated between the terminals, making them difficult to access, an AFP correspondent reported.
Netanyahu's flight was delayed by five hours as he held talks with his coalition partners.
President Isaac Herzog, who holds a largely ceremonial role, has for weeks been toiling over a proposal to soften the government's legal overhaul.
'Worst possible time'
The controversy in Israel puts Germany in an uncomfortable position.
Germany and Israel forged strong diplomatic ties in the decades after World War II, with Berlin committed to the preservation of the Israeli state in penance for the Holocaust.
Successive German governments have described Israel's national security as a crucial foreign policy priority.
On the eve of Netanyahu's departure for Germany and ahead of a planned trip to Britain, 1,000 writers, artists and academics wrote to the two nations' ambassadors urging their governments to scrap the visits, denouncing what they called his "dangerous and destructive leadership".
In Frankfurt, Meron Mendel, who heads the Anne Frank educational centre named for the teenage Holocaust victim, also said Berlin should have declined the visit.
"If an Israeli prime minister wants to get rid of common democratic values, then today is the worst time possible to invite him to Berlin," Mendel told public broadcaster Bayerischer Rundfunk.
Some Israelis living in Berlin have also called for protests against the visit, including a demonstration at the Brandenburg Gate on Thursday.
Government spokesman Steffen Hebestreit on Monday said Netanyahu is the "elected prime minister of Israel and therefore also a normal guest in Germany".
Besides meeting Steinmeier, Netanyahu will hold separate talks with Chancellor Olaf Scholz.
According to Netanyahu's office, the two "will discuss diplomatic and security issues, first and foremost the Iranian issue, as well as regional developments".
It said the Israeli leader would "stress the need to prevent Iran from obtaining nuclear arms".
The meeting with Scholz is the first in their current roles, "and an expression of the special relations between Israel and Germany, and of the cooperation in a range of fields", added Netanyahu's office.