In a phone call on Monday, Mr. Biden warned Mr. Netanyahu that he could fend off criticism of the Gaza strikes for only so long, according to two people familiar with the call. That conversation was said to be significantly stronger than an official summary released by the White House. It affirmed Israel’s right to self-defense and did not repeat calls by many congressional Democrats for an immediate cease-fire. The phone call and others since the fighting started last week reflect Mr. Biden and Mr. Netanyahu’s complicated 40-year relationship. It began when Mr. Netanyahu was the deputy chief of mission at the Israeli Embassy in Washington and Mr. Biden was a young senator with a passion for foreign affairs. Since then, they have rarely seen eye to eye, but have forged an occasionally chummy working relationship through seven American presidencies — Mr. Netanyahu has been prime minister for four of them — and raging political battles over the Iran nuclear deal and Israeli settlement policy.