WASHINGTON — Vice President Joseph R. Biden Jr. announced on Friday that he would not attend the speech to Congress by Prime Minister Benjamin Netanyahu of Israel next month, further escalating a diplomatic flap that has already soured relations between the Obama administration and one of America’s closest allies.

Mr. Biden, who as president of the Senate would normally be seated next to the House speaker during such a speech, plans to be overseas when Mr. Netanyahu visits, his office announced. President Obama had already decided that he would not meet with Mr. Netanyahu, citing a policy of not getting together with foreign leaders shortly before elections in their countries.

There have been deepening strains between the Israeli leader and the administration since Representative John A. Boehner, the House speaker, arranged for Mr. Netanyahu to address Congress about Iran without informing the White House. Mr. Netanyahu is deeply worried about Mr. Obama’s efforts to negotiate a nuclear pact with Iran, and Republicans want to give him a forum to express those concerns.

It has driven a partisan wedge into what has traditionally been bipartisan support for Israel. Democrats in Congress have expressed anger over the speaking invitation, and some have talked about skipping the speech. Israeli officials were on Capitol Hill this week to try to calm Democrats, and some said they thought most would still attend. But Mr. Biden’s decision could encourage others to boycott.