Clark writes that the current conflict in Israel and Gaza is of concern to anyone who believes in democracy and human rights.
"While the world watches in agony, we recognize the need for a ceasefire that leads to long-term security and peace in the region," she writes in the letter posted Sunday to the website of The Centre for Israel and Jewish Affairs.
"Israel has the right to defend itself and its citizens against terrorist attacks."
The letter was read aloud to a gathering of nearly 1,000 people on Sunday at the Temple Sholom synagogue in Vancouver and received an ovation, said Darren Mackoff, director of The Centre for Israel and Jewish Affairs.
It coincides with a trip by six Canadian parliamentarians to Israel, arranged by the centre, to gain firsthand knowledge on the conflict between Israel and Hamas. And it echoes the stance taken by Prime Minister Stephen Harper and Foreign Affairs Minister John Baird that Israel has a right to defend itself.
"(Clark's letter) means a lot. We don't feel as alone when we get that kind of support," Mackoff said. "The premier's statement is incredibly important to us, just as the statements of support across the political spectrum and across the Canadian spectrum."
In the letter, Clark calls Israel a "culturally rich democratic nation" committed to maintaining the rights of its citizens "regardless of gender or religion."
"Support for Israel abroad makes a difference," she writes. "As the world continues to hope for a peace that satisfies both Israelis and Palestinians, I'm proud that British Columbia can be counted as a friend of Israel."
A spokesman for Clark said the premier wasn't available for an interview, but explained the letter was sent in response to a request for a letter made last week by the Jewish Federation of Greater Vancouver.
Clark's letter was posted online as a ceasefire continues to appear elusive after more than three weeks of fighting between Israel and Hamas in Gaza.
Palestinians say the conflict has already killed at least 1,050 Palestinians, while Israel says the battle has claimed 52 of its soldiers and three civilians.
"It is a natural fit for (Clark) to comment on this as she has in the past," Mackoff said, adding he would "categorically dismiss" any insinuation the letter was politically motivated.
"The premier is not running for re-election at the moment," he said. "This is about doing the right thing and standing up for what you believe in."
The chairman of the Canada Palestine Association strongly disagreed.
Hanna Kawas called the contents of the letter "outrageous" and said he believes Clark's decision was based on winning votes from the Jewish community.
He said the premier had no business wading into the issue, noting she was elected on a platform of standing up for B.C. families.
"She would do better if she would solve the teachers' strike rather than (using) our taxpayers money in dealing with international issues," said Kawas, whose Vancouver-based organization was formed in 1980 and represents about 5,000 people in B.C. and many thousands more across the country.
Kawas said Clark's statement is based on ignorance of the facts on the ground and said she should not be speaking on behalf of British Columbians on the matter. He added that a comment he made below the letter on the Jewish group's website was deleted.
"We have enough people who don't know what they're talking about in Ottawa, so we don't need more people who really don't know what they're talking about in B.C.," he said.
On Monday, Israeli Prime Minister Benjamin Netanyahu told citizens to prepare for a prolonged war.
The day was also marked by heavy Hamas-Israeli fighting, in which Palestinian health officials said nine children were killed by a strike on a Gaza park.
Follow @TamsynBurgmann on Twitter
Note to readers: This is a corrected story. An earlier version incorrectly called the gathering at the Temple Sholom synagogue one that was held to celebrate Israel's national independence day.
Also on HuffPost