A plan to extend the deadline for illegal aliens to apply for amnesty was in limbo Thursday after a Republican senator blocked the measure from coming to a vote.

In blocking Democratic attempts to bring the extension to a vote Wednesday night, Sen. Phil Gramm, R-Texas, said the plan to extend the deadline from May 4 to Nov. 30 would "send the wrong signal around the world."If Gramm or another senator continues Thursday to block the vote, the soonest the Senate could move to cut off debate would be Friday.

Gramm said there has been "a mammoth increase in the number of people entering the country illegally" in the past year because word spread that a tough new immigration law would not be enforced.

"If we came in now and changed the law on the very eve of it going into effect, the net result would be to cast further doubt on the credibility of the law and that would bring numerous people across the border illegally," Gramm said.

"We extended the deadline for taxes, why not amnesty?" asked Sen. Edward Kennedy, D-Mass. "The May 4 deadline has turned out to be too short and too harsh. A refusal to extend it is cruel and vindictive."

The House passed the extension 213-201 last week, a majority much too small to override a threatened presidential veto.

Under the law, aliens who came to the United States illegally but have lived here continuously since before Jan. 1, 1982, were given one year to apply for temporary residency as the first step toward permanent status. That 12-month deadline is May 4.