Senate Democratic leaders have decided they will not publicly release a health care reform letter signed by their rank and file intended to calm nervous House Democrats before their historic vote this weekend on the comprehensive Senate-passed measure and a budget reconciliation bill of fixes.

Sources said a handful of Democratic Senators asked Senate Majority Leader Harry Reid (D-Nev.) to keep the letter private. The missive laid out a set of principles that Senatorial signatories would pledge to support in the health care reconciliation bill, which will need to be passed by the Senate after House action.

“The purpose is to give assurances to the House, and that can be done privately,” said one senior Senate Democratic aide.

Reid spokesman Jim Manley declined to comment except to say that Democratic leaders are “confident that the House understands the Senate is prepared to deliver.”

One senior House Democratic source said the letter had not yet been delivered to the chamber.

And one Senate Democratic source indicated that Reid had not yet been able to round up the 51 signatures he needed to provide the assurance that the Senate would be able to pass the reconciliation measure. However, the source cautioned that the inability to get 51 votes was not because Reid didn’t have personal commitments from 51 or more Senators, but because many Democratic Senators are squeamish about sticking their necks out before the House has passed the bill.

If the House passes both measures this weekend, the Senate will take up the reconciliation bill next week.