WASHINGTON (AP) — A Democratic bill enhancing health care, education and job-training benefits for veterans faces an uphill climb as the Senate approaches a showdown vote on the $21 billion legislation.

Both political parties generally favor helping the nation's 22 million veterans and their families, especially in a congressional election year. But Republicans consider the wide-ranging legislation too expensive, and they also want to add a provision imposing new sanctions on Iran for its nuclear program.

Senate Majority Leader Harry Reid, D-Nev., has blocked a vote on a GOP alternative eliminating some of the improvements and slapping the sanctions on Iran. Citing Reid's move, Republicans were expected to rally behind a procedural effort Thursday to derail the veterans bill — and each party accused the other of seeking partisan gain.

President Barack Obama strongly opposes the additional sanctions, saying international talks on Iran's nuclear program must be given more time. Similar, bipartisan Iran legislation drew 59 Senate co-sponsors, and a vote potentially could embarrass the White House.

Sen. Bernie Sanders, I-Vt., chairman of the Senate Veterans Affairs Committee, said it would be "extremely disrespectful to the men and women who have put their lives on the line" to block the massive measure because of the dispute over Iran.

"The American people don't want to see serious legislation sabotaged because of political partisanship," Sanders said.

Republicans accused Reid of blocking them from shaping bills and said he was shielding Democratic senators from a difficult vote.

"What Reid would like to do is take all the votes and push them past the November election," said North Carolina Sen. Richard Burr, top Republican on the Veterans panel.

It will take 60 votes to keep the bill alive — more than the 53 Democrats and two Democratic-leaning independents are likely to garner.

The bill would make many veterans without service-connected injuries eligible for treatment at VA medical facilities. It would expand the dental, chiropractic and fertility treatments the VA provides, bolster programs for veterans who suffered sexual abuse and increase the use of alternative medicine such as yoga for stress.

More veterans would be eligible for in-state tuition at public universities. Some benefits for spouses of deceased veterans would improve, and aid to relatives caring for a wounded veteran would be expanded to include those who served before the terrorist attacks of Sept. 11, 2001.

The Veterans Affairs Department would be required to publicly report more data on its handling of veterans' benefit claims. That and other steps are designed to eat into the VA's backlog of 390,000 claims that have been awaiting action for more than 125 days.