Ports security legislation that most senators agree would make the country safer was stuck Tuesday in election-year politics as Republicans threatened to scrap it if Democrats forced in a wide range of provisions.

It was unclear when the Senate would vote — if ever — on the bill that as recently as last week was considered a sure thing.

The Democratic plan "will kill the bill," said Sen. Ted Stevens, R-Alaska. "We have a bipartisan bill to start with. ... All these amendments are just coming out of the sewer right now. There's just too many of them, and they're just nothing but attempts to block this bill."

Senate Democratic leader Harry Reid said his plan would also bolster security on trains and buses and at chemical plants, strengthen U.S. intelligence missions overseas and approve all of the 9/11 Commission's recommendations, half of which are still undone.

"Let's see if they'll vote against this," said Reid, D-Nev., hoisting a thick stack of white papers.

Reid acknowledged that the port security bill, even without his additions, would be better than nothing. "But why don't we try to improve that? And that's my point. Try to improve it. That's all I'm trying to do," he said.

Voters have ranked national security among top election concerns this fall, which marks the fifth anniversary of the 9/11 terror attacks, and candidates from both parties are scrambling to portray themselves as stronger on the issue than their opponents. Congress made port security a particular priority after a February fight over a buyout that put a Dubai company in control of some operations at six American ports.

The Democratic plan would put Republicans in the awkward position of voting against security measures that many voters believe are long overdue.

Stevens, however, said the plan would delay progress on port security, including putting monitors at the nation's 22 largest seaports to screen for materials to make radiological "dirty" bombs or nuclear weapons. The bill would have to be considered by multiple congressional committees to work out differences between House and Senate bills, he said.

David Heyman, homeland security director at the Center for Strategic and International Studies, said the flare-up could scuttle the entire bill.

"Everybody wants to go back to their constituents and say they've done something to make us more secure," Heyman said. "If something gets done, everybody benefits. But if nothing gets done, Democrats will benefit because if you look at polls, people believe Congress isn't doing its job, and voters want change."

Homeland Security Secretary Michael Chertoff, testifying before a Senate panel earlier Tuesday, urged lawmakers to approve the port security legislation, calling it "a tremendous contribution" to measures the Bush administration has already undertaken.

As part of the bipartisan ports security bill, senators also approved requirements Tuesday for the government to send emergency alerts to cell phones and pagers. They were considering Tuesday night whether to eliminate a hiring cap on Transportation Security Administration screeners and hire an additional 1,000 Customs and Border Protection officers.