As the federal citizenship agency and the FBI say they are picking up the pace to eliminate a backlog of citizenship applications, immigrants anticipating decisions on petitions they filed months, and in many cases years, earlier shouldn’t necessarily be resting easier.

Some lawyers who handle naturalization cases say U.S. Citizenship and Immigration Services adjudicators appear to be more eager to reject citizenship applications of late, meaning some of those aiming to be citizens in time to vote in the presidential elections in November may find themselves left out.

“We expect that a lot of people will be disappointed,” a partner at the immigration law firm Wildes & Weinberg, Michael Wildes, said. “We see the government denying cases left and right.”

The number of denials on dubious legal grounds seems to have ticked upward, according to some lawyers in New York.

An immigration attorney at the firm Bretz & Coven, Matthew Guadagno, said he has handled a slew of recent cases in which he said applicants were denied unfairly for long-ago criminal convictions or for mistakes on their application forms, which he says the USCIS sometimes labels fraud even if the mistakes are inadvertent.

In one case, he said a New York City developer who builds low-income housing was denied based on a minor criminal conviction from his past.

Lawyers say the immigration agency is only supposed to look at crimes committed in the past five years, unless a past crime is particularly egregious. The agency says it is allowed to include other older crimes, however, if they seem to establish a pattern of “bad moral character.”

Mr. Guadagno said he won the developer’s case by appealing in federal court, and said he has won many others like it.

“When there is a denial, it’s usually problematic,” he said of the cases his firm has seen. “All of the clients were very successful, and were very accomplished, and that’s why they wanted to naturalize.”

An immigration lawyer who has also worked as an assistant U.S. attorney in Brooklyn, Michael DiRaimondo, said he recently handled the cases of a husband and wife who applied for citizenship after both had been convicted on one count of petty larceny in the 1980s. The wife was accepted, but USCIS denied the husband.

Mr. DiRaimondo said he later won the husband’s case in federal court.

The agency has not seen a “notable increase in requests for the federal court in New York to review decisions to deny applications for naturalization,” according to a spokesman, Shawn Saucier.

Although lawyers say many applicants have a good chance of fighting back, for some, appealing a denial in federal court is not always an option.

Before they can go to federal court, immigrants must first bring an administrative appeal within the agency. The fee to appeal more than doubled last summer, to $605 — an increase that has received less notice than the increase in the original application fee, to $675. To take a case to federal court costs much more.

An immigration expert at the New York University School of Law, Nancy Morawetz, has also criticized the functioning of the judicial appeals mechanism in some cases.

“If they deny you, then they get to depose you and everyone you know before you become a citizen. They don’t get reviewed for their illegal denial,” Ms. Morawetz, who directs the law school’s Immigrant Rights Clinic, said. “Our system is based on the idea that those who meet the criteria should be approved, not that they should go through endless hurdles.”

Many of the applicants currently waiting for decisions were encouraged to apply during a national campaign by Hispanic groups last year in preparation for the upcoming presidential election.

When there are waves of new applications, as there was last summer during the Hispanic get-out-the-vote campaign and before the USCIS implemented a fee increase, Mr. Saucier said there are generally more people rejected.

“We have noticed when there is an increase in citizenship applications, such as July of 2007, we also see an increase in the number of people applying who really are not ready to apply,” he said.

He added that this assessment does not necessarily include the separate set of people whose applications have been held up by FBI security checks and who may have their cases decided soon. He also noted that an application delayed by a name check would not be adversely affected, unless the check turns up evidence of bad moral character.