ABC News' Shushannah Walshe and Michael Falcone report:

Make up your mind. That's the message an influential Kentucky congressman is sending to a fellow Bluegrass State Democrat who has spent months contemplating whether to challenge Senate Minority Leader Mitch McConnell but has yet to announce her intentions.

Three-term Rep. John Yarmuth, the state's only Democratic congressman, had some blunt advice for the potential Senate contender, Secretary of State Alison Lundergan Grimes, in an interview with ABC News on Tuesday.

"It's very important to do it now," Yarmuth said, adding that he and other prominent Democrats have been reaching out to Grimes but not getting much of a response. He called her failure to return calls "extremely unusual."

"She's keeping her own counsel on this, and I guess that is fine, but there are others waiting in the wings," Yarmuth said, noting that Democrats want to "avoid an expensive primary."

In fact, in a separate interview with the Kentucky radio station, WFPL, published Tuesday Yarmuth went so far as to say Grimes' foot-dragging was "a disservice to the party."

Despite the pressure, an adviser to Grimes said she would not be rushed into making "a snap decision."

"She's certainly closer to making a decision than she has been because she has been talking to a lot of people and assessing what this opportunity means," the adviser told ABC News. "I would think in the not-too-distant future you will hear an answer from her," noting an announcement was likely to come within a month.

Grimes' spokeswoman, Lynn Zellen, said in a an e-mail message to ABC News last week that "Secretary Grimes is continuing to talk with her supporters across Kentucky and giving it the due diligence it deserves."

And not all Democrats agree with Yarmuth's assessment.

"There is no mounting pressure in terms of the timeline. The examples are numerous of candidates getting in much, much later and being successful," one Democratic strategist said. "Resources do become an issue, however a Democratic candidate will have no problem raising money at the prospect of defeating Mitch McConnell."

Kentucky's Senate contest is hardly the only 2014 race that is not yet fully formed. Even so, waiting much longer, Yarmuth warned, would take up valuable "time another candidate would want to take advantage of" especially against McConnell who has been busy fattening his campaign war chest and producing positive ads, which are running online and on television.

Grimes' indecisiveness recently led National Republican Senatorial Campaign Committee strategist Brad Dayspring to label her "the reluctant candidate."

Earlier this year, Democrats seemed to be hanging their hopes of defeating McConnell on actress Ashley Judd, but Judd announced in late March that she would not run.

From Louisville to Washington, DC, McConnell's opponents have placed an enormous target on his back. And Yarmuth, who vocally promoted Judd's potential candidacy, isn't the only Democrat nudging Grimes in the direction of running. The group, Emily's List, appeared to all but endorse the not-yet-declared Grimes on Tuesday.

"Allison Grimes is an impressive candidate who would bring a refreshing perspective to end the Mitch McConnell era of gridlock and partisan politics in Washington," spokeswoman Marcy Stech said in a statement. "We are excited about her potential run and an opportunity to send McConnell packing."

Also on Tuesday, the pro-Democratic Senate Majority PAC was touting the results of a survey it sponsored, conducted by Public Policy Polling, showing a tight head-to-head matchup between Grimes and McConnell.

Former Miss America Heather French Henry, wife of former Lt. Gov. Steve Henry, has also said she is "seriously considering" entering the race and Yarmuth said she plans to announce a decision this week whether Grimes does or not. Other possible candidates include Bill Garmer, an attorney and former state Democratic Party Chairman, and Tom Fitzgerald, an environmental attorney.

Should Grimes decide to run, Yarmuth said "she won't have a more enthusiastic supporter" than he, but in the interview, he was also candid about the challenges Grimes would face.

"She's a very good retail politician - she proved that. She has a statewide organization, a network of supporters - that's very important. She has great contacts with her father and the Clintons. That's very, very important," the third district congressman said. "But the downside is she's young, she really doesn't have much of a record and she's going to have to get up to speed on federal issues pretty quickly."

Yarmuth's bottom line: time is of the essence.

"There aren't many Ashley Judds out there who can jump in the race in January and have enough name recognition and access to resources that they can run a successful campaign," he said.