WASHINGTON — When the Obama administration wanted to be certain that Congress would not block $50 million in new aid to the Palestinian Authority last month, it turned to a singularly influential lobbyist: Israel’s prime minister, Benjamin Netanyahu.

At the request of the American Embassy and Secretary of State Hillary Rodham Clinton, Mr. Netanyahu urged dozens of members of Congress visiting Israel last month not to object to the aid, according to Congressional and diplomatic officials. Mr. Netanyahu’s intervention with Congress underscored an extraordinary intersection of American diplomacy and domestic politics, the result of an ever-tightening relationship between the Israeli government and the Republican Party that now controls the House.

On Tuesday, one of President Obama’s potential rivals in 2012, Gov. Rick Perry of Texas, delivered a speech in New York criticizing Mr. Obama’s stance toward Israel as “naïve, arrogant, misguided and dangerous.” Mr. Perry said that he would be a guest soon of Danny Danon, the hard-right deputy speaker of the Israeli Parliament.

The relationship between the Israeli government and the Republican Party has significantly complicated the administration’s diplomatic efforts to avert a confrontation at the United Nations this week over the Palestinian bid for full membership as a state, limiting President Obama’s ability to exert pressure on Mr. Netanyahu to make concessions that could restart negotiations with the Palestinians.