President Bush will likely cast the first veto of his presidency if the Senate, as expected, passes legislation to expand federal funding of embryonic stem-cell research, White House aide Karl Rove said Monday in Denver.

"The president is emphatic about this," said Rove - Bush's top political adviser and architect of his 2000 and 2004 campaigns - in a meeting with The Denver Post editorial board.

The U.S. House of Representatives voted 238-194 last year to pass the legislation, co-sponsored by Rep. Diana DeGette, D-Colo., and Rep. Mike Castle, R-Del. If the Senate approves the bill, it will go to the president's desk.

Senate Majority Leader Bill

Frist, R-Tenn., who backs the bill, has said he will try to bring it up for a Senate vote soon.

"It is something we would, frankly, like to avoid," Rove said when asked if the White House would welcome, or dread, vetoing legislation passed by a Republican Congress, especially on such an emotional issue as embryonic stem-cell research.

But Rove said he believes the legislation will pass the Senate with more than 60 votes this month, "and as a result the president would, as he has previously said emphatically, veto the Castle bill."

"I'm appalled that Bush would use the first veto of his presidency to veto a bill that could help 110 million people and their families," DeGette said Monday of Rove's remarks.

On another volatile issue - congressional attempts to reform the nation's immigration system - Rove said immigration legislation had to be "comprehensive" to win Bush's support but that more controversial proposals such as a temporary- worker program might be phased in as the U.S. improves its border security.

Rove said House and Senate negotiators were making "good" progress toward

an immigration compromise and that there is still a chance that a bill could be passed before the November election.

In a wide-ranging 90-minute interview, Rove also defended the Bush administration's policy in Iraq and predicted that Republicans would maintain control of both the House and the Senate in the November election.

The Bush administration's stem-cell policy, adopted in 2001, has been to allow federal research funding only for existing lines of embryonic stem cells.

Researchers and patient groups have complained that the policy hinders vital research into treatments for diabetes, Parkinson's disease and other illnesses.

Colorado Springs-based Focus on the Family is among many conservative and anti- abortion groups opposed to the measure.

Rove said backers of the stem- cell bill lack the votes needed - two-thirds of each house of Congress - to override a veto.

"We were all an embryo at one point, and we ought to as a society be very careful about being callous about the wanton destruction of embryos, of life," Rove said.

Recent studies, he said, show that researchers "have far more promise from adult stem cells than from embryonic stem cells."

If Bush vetoes the bill, "we will try to override it," DeGette said, adding that support among lawmakers is growing.

Castle and DeGette have requested a meeting with Bush to present their case.

"I still hold out hope that the president would give us that courtesy for a meeting," she said.

Rove was in Colorado to speak Sunday at an Aspen Institute forum and to attend several political events, including a Republican gathering Monday night near Parker.

Addressing immigration at the editorial-board meeting, Rove was receptive to proposals by some congressional Republicans to establish checkpoints at ports of entry to the U.S., where existing illegal immigrants would have to go to register, pay a penalty and show proof of employment.

He said such checkpoints didn't necessarily have to be on the border but could be located at airports in Denver or Los Angeles, for example, or at ports of entry such as New Orleans.

Comprehensive reform is needed because illegal immigrants will find ways to enter the United States as long as wages are high here when compared with other countries.

"You cannot control the border. ... We don't have enough resources," he said. "You've got to do it all together."

Rove said he advises GOP candidates to back the president's comprehensive approach, despite the fierce opposition of Republican hard-liners such as U.S. Rep. Tom Tancredo of Colorado.

"I cannot see a single district in which a Republican is going to be advantaged by opposing a comprehensive solution," said Rove.

When asked about the November election, Rove was confident that the Republicans will weather the recent dip in the polls.

He made the same remarks rallying Republicans at an event near Parker on Monday night.

Meeting with more than 200 supporters at the Colorado Wildlife Experience, Rove urged them to vote for Republican candidates for Congress and the governor's office.

To rousing applause, he focused his speech on the economy and the war on terrorism.

"All that we asked is to be judged by the results," he told them.

Staff writers Manny Gonzales and Christa Marshall of The Denver Post contributed to this report.