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(CNN) -- Wisconsin Gov. Scott Walker's administration on Friday issued notices to unions, warning them of possible layoffs in early April if the budget impasse continues.

The measure "may be able to be rescinded and layoffs avoided" if 14 Senate Democrats return to the state Capitol, the Republican's office said in a press release.

"Without Senate action within 15 days, individual employees may begin to receive potential termination notifications," said spokesman Cullen Werwie.

Walker has warned that the state might have to lay off 1,500 state workers if the Democrats don't return to meet a quorum to vote on Walker's so-called budget repair bill. The initiative would restrict the collective bargaining rights of many public employees, as well as require state workers -- with the exception of police and firefighters -- to cover more of their retirement plans and health care premiums.

Republicans need a single Democrat to cross party lines and rejoin the 33-member legislature to meet the quorum of 20 lawmakers required in a vote on state fiscal matters. Only 17 lawmakers are required for most other issues.

Letters to 13 public union heads, sent Friday by State Employment Relations Director Gregory Gracz and released by Walker's office, state that "agencies must take action to decrease their expenditures to make up for the savings lost due to" the delay in the vote on the governor's bill.

While stating the cuts would not take effect before April 4, the letters don't specify exactly how many unionized employees could lose their jobs. Walker's office explained that individual employees had to be given a two-week notice before any "permanent" layoffs.

Meanwhile, the state Senate has approved a resolution that would hold absentee Democratic lawmakers "in contempt of the Senate." The measure allows state law enforcement to detain the Democrats and bring them back to Wisconsin, according to Andrew Welhouse, a spokesman for Wisconsin Senate Majority Leader Scott Fitzgerald.

But whether the contempt measure is constitutional remains unclear. The state constitution prohibits the arrest of lawmakers while the legislature is in session, except for "treason, felony and breach of the peace."

Whether Wisconsin law enforcement would be permitted jurisdiction in Illinois to detain the missing lawmakers is also unclear.

Democrat State Sen. Jon Erpenbach said Friday that the move threatened to derail any productive discussions between fellow Democrats and Republicans, including representatives from the governor's office.

"We were pretty close to an agreement" but "then the Senate puts out arrest warrants," he said, blaming Senate Republican leadership for impeding negotiations.

The stalemate has appeared increasingly contentious in recent days as Senate lawmakers adopted a resolution Wednesday that would fine absentee lawmakers $100 every day they remain missing.

A similar resolution passed a day later in Indiana, where House Republicans have imposed a $250-a-day fine against the AWOL Democrats who -- like their Wisconsin counterparts -- fled to Illinois in protest of a labor bill.

Walker's budget-repair bill has drawn fierce and spirited opposition from unions, Democrats and others, hundreds of whom have demonstrated inside and outside the state Capitol in recent weeks in Madison. Some of them even slept inside of the building, prompting an order Thursday from Wisconsin Circuit Court Judge John Albert that barred demonstrators from staying in the state Capitol after business hours.

On Friday night, the state's Department of Administration noted on its website that the Capitol closed at 6 p.m., with Capitol Police Chief Charles Tubbs speaking to five people who left shortly thereafter.

Some 4,653 people visited the building on Friday -- about four times more than the previous day. One person was arrested for trying to bypass weapons screening despite repeated warnings, according to the state agency. The Capitol will be open from 8 a.m. to 4 p.m. Saturday and Sunday, with more large crowds expected.

A Wisconsin Democrat was tackled by Capitol police Thursday night as he tried to walk through a door in the state legislature, which has been closed to the public.

Nick Milroy, an assembly member, admitted Friday that he was "aggressive in attempting to re-enter the Capitol, and law enforcement was aggressive in trying to keep me out."

"This armed-palace environment created by Gov. Walker has everyone feeling very tense, and emotions are running high," Milroy said of the incident, captured on camera by Milwaukee-based WISN-TV.

Police closed the facility after crowds demonstrated in and around the building, contributing to $6.5 million in damage and other costs since mid-February, according to Administration Secretary Mike Huebsch.

Milroy "was attempting to gain access without showing his ID," said Huebsch. He "was using his own political agenda to get himself arrested and make a point."

The state is confronted with a looming $137 million shortfall at the end of the fiscal year, June 30. The state faces a $3.6 billion budget gap by 2013.

CNN's David Mattingly, Eric Fiegel and Katherine Wojtecki contributed to this report.