WASHINGTON - Republican and Democratic senators Sunday questioned how former Sen. Tom Daschle could make a $128,203 mistake on his taxes but said they were not prepared to oppose his nomination as health secretary.

"You have to be troubled by it," said Sen. Jon Kyl of Arizona, the No. 2 Republican in the Senate.

"We'll have to question former senator Daschle and understand his explanation, and then have a conversation about it and see where it goes," Kyl said on "Fox News Sunday." As to how much trouble the tax issue could present for the nomination, he said, "I think it's too early to tell."

Daschle recently filed amended tax returns to report $128,203 in back taxes and $11,964 in interest. The amended returns reflect additional income for consulting work, the use of a car service and reduced deductions for charitable contributions.

The South Dakota Democrat, once the majority leader of the Senate, was scheduled to meet privately Monday with the Senate Finance Committee.

Senate Republican leader Mitch McConnell of Kentucky said he was surprised that Daschle had not paid his taxes properly but would not say whether he thought the nomination was in trouble. He said the committee will make a recommendation to the full Senate. "I think I'm going to just wait until they give me their opinion," he told CBS' "Face the Nation."

Sen. Jim DeMint (R-S.C.) said the problem could disqualify Daschle but that he wanted to learn more about the matter.

"It's disheartening, obviously. People are struggling to pay taxes on a very small amount of income and he's got this huge amount," DeMint said on ABC's "This Week."

Sen. Susan Collins, a Maine Republican, also said the tax problem was a concern and needed more explaining, telling CNN's "State of the Union" that it involved "an awful lot of money" but that she had not decided to vote against confirmation.

On the Democratic side, Sen. Ben Nelson of Nebraska called it "a tough issue" and said he was waiting to hear the results of the meeting between Daschle and the Finance Committee.

"I'm not prepared at this point in time to vote no," Nelson told CNN.

The Senate's No. 2 Democrat, Dick Durbin of Illinois, defended Daschle but said skepticism, even cynicism, about Daschle not paying his taxes was understandable.

"But if you know Tom Daschle, you know better," Durbin said on Fox. "He's found himself having made a mistake and admitted to it. He took the steps necessary to start paying the taxes, make sure they're paid. Now, that's the right thing to do. I believe Tom Daschle's one of the most honest people I've ever known or worked with in public life."

Daschle, chosen by President Obama to lead the administration's health initiatives, is the second cabinet nominee to scramble to pay back taxes. Timothy Geithner's confirmation as treasury secretary was delayed after it was revealed that he had failed to pay more than $34,000 in taxes.

Obama's first choice for commerce secretary, New Mexico Gov. Bill Richardson, took his name out of consideration when his confirmation appeared headed toward complications because of a grand jury investigation over how state contracts were issued to political donors.

"President Obama wanted to have a very ethical administration starting out and so on, but I think he's seeing how hard it is to avoid these kind of problems," Kyl said. "And I just wonder, if president Bush had nominated these people, what folks would be saying about that."