The bipartisan group of eight senators drafting immigration overhaul legislation is still haggling over the details of its bill but hopes to make its self-imposed deadline of early April, members said Wednesday.

Arizona GOP Sen. John McCain, speaking at a press conference near the U.S. border in Nogales, Ariz., noted that the bill is being written in a bipartisan manner with the intention of winning as many votes as possible.

“Nobody is going to be totally happy with this legislation,” McCain said. “No one will be because we are having to make compromises, and that’s what makes for good legislation. It’s compromise that brings everybody together.”

Sen. Charles E. Schumer, D-N.Y., who attended the press conference after touring the border at McCain’s invitation, said the gang of eight is “very close” to finalizing the bill.

“I’d say we are 90 percent there,” Schumer said. “We have a few little problems to work on; we’ve been on the phone all day talking to our other four colleagues who aren’t here.

“We are very hopeful that we will meet our deadline, we believe we will meet our deadline; we are on track to meet our deadline of having a bill when we get back to Congress in a couple of weeks,” Schumer said.

He declined to provide any other details of the negotiations.

Two other members of the gang of eight — Sen. Jeff Flake, R-Ariz., and Sen. Michael Bennet, D-Colo. — also attended the fact-finding trip and press conference. The remaining four members of the group — Senate Majority Whip Richard J. Durbin, Sen. Robert Menendez, R-N.J., Sen Lindsey Graham, R-S.C., and Sen. Marco Rubio, R-Fla. — did not attend.

“They wanted to come … but they had already made plans for this recess,” McCain said.

Members of the group have been working on the bill since January and have been reluctant to give themselves a more specific deadline, arguing the package is complicated.

Nevertheless, pressure is mounting for Congress to act on the issue before the end of the summer. Senate Judiciary Committee Chairman Patrick J. Leahy, D-Vt., has said he intends to take up the bill as soon as possible, but has also expressed concern that the delay in unveiling a bill has made it difficult to clear the bill before the end of April.

Some Republican members of the committee, who have called for patience on the issue, are concerned Leahy will seek to rush the bill.

President Barack Obama has also recently called on Congress to pick up the pace on immigration reform. Earlier this year he said he would put out his own bill if the Congressional process takes too long, but he has declined to say when exactly he wants to see a bill.

Schumer said the Nogales trip reinforced discussions with McCain and Flake that the border’s varied terrain requires different approaches and that one solution, such as building a fence, won’t work.

“We saw various, different types of fencing,” Schumer said. “And then we saw lots of areas where a fence wouldn’t be practical. … So there is not one size that fits all.”

Schumer also noted that the negotiators intend to design the bill so that it pays for itself with fees and fines — charged to undocumented immigrants — covering increased border protections.

McCain said technology would help accomplish the goal.

“The main thing we are going to try to see deployed is technology,” McCain said. “Surveillance capability both on the ground and in the air, that lessens requirement for roads or people.”

The group’s bill is also expected to make the path to citizenship for illegal immigrants contingent on whether the border is secure.

“I believe if we do the right thing … that over a relatively short period of time, with the proper use of technology, with the proper coordination with different agencies that we will be able to say that we have a degree of border security that would allow people to move forward to a path to citizenship,” said McCain.