“The White House and president have not been as clear as where it stands and he stands on the relationship, and that has added interest on the part of the members,” Mr. Cantor said. “With Iran continuing to pursue nuclear capabilities, and with the upcoming vote in the U.N., which is a very destabilizing event, it is very important for us to be there and show what is at stake.”

The weeklong trips began earlier in the month with 26 Democratic members, who were accompanied by Representative Steny H. Hoyer of Maryland, the minority whip, and are continuing over the next several days with 55 Republicans, who arrive in two delegations. (Mr. Cantor, the majority leader, will spend time with both.)

The trips’ schedules include visits to both Israel and the West Bank, as well as meetings with President Shimon Peres and Mr. Netanyahu in Jerusalem, and with the Palestinian Authority’s president, Mahmoud Abbas, in Ramallah. For many of the lawmakers, the trip is their first time in Israel.

“It’s my responsibility to be able to advocate on pro-Israel issues,” said Representative Michael Grimm of New York, a freshman who went with the first group of Republicans, in a telephone interview from the country. “Coming here and being able to feel it and touch it to fully understand how daily life is for an Israeli is important. You have to actually see it and realize it is such a profound observation that everything is so close; everything is almost on top of each other.”

The trips have attracted criticism from a variety of groups, including supporters of the Palestinians and critics of American foreign aid, especially that for Israel. But in a rare show of bipartisanship, both Republicans and Democrats defended the trip.