BOSTON - Paul Kirk, a former Democratic National Committee chairman and a close friend of the late Senator Edward Kennedy, was named on Thursday as a temporary replacement for the liberal champion in the U.S. Senate.

Kirk, an attorney backed for the post by Kennedy's wife Victoria and his two sons, will fill the seat until voters in Massachusetts elect a permanent replacement in January.

The appointment of Kirk, who said he would not run in the special election, will restore a 60-seat Senate majority for the Democrats that could help President Barack Obama's push to overhaul healthcare.

Obama called Kirk an excellent interim choice to take over from Kennedy and give his state its full representation in the Senate as healthcare, financial reform and energy issues are debated in the coming months.

Republicans in the overwhelmingly Democratic state sought an injunction to stall the appointment, saying legislation just passed to allow the move should not take effect for another 90 days. A judge in Boston will hear the request on Friday.

Lawmakers in Massachusetts passed legislation in the past few days allowing Governor Deval Patrick to name an interim senator, something Kennedy pushed for before he died in August from cancer so his party would not lose a key vote during the healthcare debate.

The issues before the Congress and the nation are too important for us to be one voice short, Patrick told reporters as he appointed Kirk after signing the legislation.

Kirk was Kennedy's special assistant in the 1970s and remains close to his family.

Kennedy was a towering figure in the U.S. Senate for nearly half a century and made healthcare reform his signature issue as he carried on his storied family's political legacy.

Without an interim replacement, his seat would have lain vacant until a January 19 special election of a permanent senator to serve through 2012.

Kirk, 71, who served as chairman of the Democratic National Committee from 1985 until 1989, was seen as a natural candidate to take over the Senate seat. An eloquent speaker who was master of ceremonies at a memorial service for Kennedy last month, he has in-depth knowledge of Washington politics and backs Obama's plans to overhaul the ailing $2.5 trillion healthcare system.

Kirk called the interim Senate appointment a profound honor and the Kennedy family said nothing could be more fitting than for him to fill Edward Kennedy's seat.

As a lawyer in the late 1990s, Kirk briefly lobbied for the pharmaceutical industry, notably for life sciences company Aventis, now Sanofi-Aventis, local media reported.

The change to state law to let an interim senator be named angered Republicans and some Democrats. They saw it as a hypocritical reversal of a law state Democrats passed in 2004 to prevent a Republican governor from naming a replacement for Democratic Senator John Kerry if he had won that year's presidential election.

Flanking Kirk as he was appointed, Kerry said he would be a superb steward in the caretaker Senate position.

(Reporting by Catherine Bremer; Editing by Bill Trott)