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"There is no reason to schedule this speech before Israeli voters go to the polls on March 17 and choose their own leadership," Kaine said in a Wednesday statement. "I am disappointed that, as of now, the speech has not been postponed. For this reason, I will not attend the speech."
Kaine joins Senate colleagues Patrick Leahy (D-Vt.), Bernard Sanders (I-Vt.) and Brian Schatz (D-Hawaii) in skipping the prime minister's address to a joint meeting of Congress. Several House Democrats have also said they are not planning on attending the speech set for Tuesday.
Netanyahu, who is set to appear at the invitation of House Speaker John Boehner on March 3, declined in a Tuesday letter an invitation made by Sens. Richard Durbin (D-Ill.) and Dianne Feinstein (D-Calif.) to meet with Senate Democrats during his trip to the Capitol.
Such a meeting, Netahyahu said in a letter to the senators, "could compound the misperception of partisanship regarding my upcoming visit."
The speech has heightened tensions between the Israeli government and the Obama administration, which was not consulted on the visit by Republican congressional leaders in what the White House has deemed a breach of protocol. Compounding the tensions is the timing of the speech just two weeks before national elections in Israel and amid multiparty negotiations over the fate of Iran's nuclear programs.
In a "Charlie Rose" appearance that aired late Tuesday, National Security Adviser Susan Rice said the planned address has "injected a degree of partisanship, which is not only unfortunate, I think it's destructive of the fabric of the relationship."
Netanyahu, in his letter, said he did not intend to give U.S.-Israeli relations a partisan gloss: "I can assure you my sole intention in accepting it was to voice Israel's grave concerns about a potential nuclear agreement with Iran that could threaten the survival of my country," he said.
But Kaine said his decision not to attend the speech was deeply rooted in the partisan implications. In a Jan. 30 letter to Boehner released by Kaine Wednesday, he urged the speaker to postpone the speech "so that Congress does not appear to be supporting a particular person or party in a foreign election."
"Congressional support for the U.S.-Israel partnership transcends any candidate or party," Kaine wrote. "Our enduring bond with Israel is underpinned by common values, democratic institutions and shared interests. ... I believe the timing of your invitation risks politicizing this long tradition of bipartisan support for the U.S.-Israel partnership."
Durbin said he was "disappointed but not surprised" that Netanyahu has declined his invitation.
"He is doubling down on John Boehner, which I think is unfortunate," he said. "There are many of us on the Democratic side who have been loyal friends of Israel long before Prime Minister Netanyahu."
Durbin, the minority whip, said he would exert no pressure on his Democratic colleagues to attend or not attend the address, calling it a "personal, individual decision."
Rachel Weiner contributed to this report.