In the letter, signed by 16 Republican and one Democrat member of the US Congress, the politicians said they were concerned that the expert group, appointed by Health Minister James Reilly to present a report on abortion, included some who are pro-choice.
The minister established the group last January in the wake of a ruling by the European Court of Human Rights that Ireland must give legislative effect to the 1992 Supreme Court judgment in the X Case which ruled that a woman was entitled to an abortion if her life was in danger as a result of her pregnancy.
The expert group, due to present its report shortly, is expected to recommend either regulation or legislation. Dr Reilly will then bring that recommendation to Cabinet.
“A concern has been expressed to us that the composition of the expert group seems predisposed to issue recommendations that infringe on the right to life, rather than a simple clarification,” says the letter.
“The absence of experts of known pro-life views and the presence of some of known pro-abortion views were especially noted,” say the members of Congress.
Among those who signed the letter is Doug Lamborn, a Republican from Colorado Springs who was forced to apologise last year to Mr Obama after saying that working with him was like touching a “tar baby”. Lamborn used the racially charged term during an interview on a Denver radio station.
The letter is also signed by Trent Franks, a Republican Congressman from Arizona, who earlier this year sought to push through legislation that would ban abortions after 20 weeks of pregnancy in the District of Columbia.
When the White House voiced opposition, Franks called Obama “the abortion president”.
The 17 Congress members say Ireland “has been an example to the world” in not legislating for abortion.
“It is our hope Ireland remains staunchly pro-life and continues to give this vital example in Europe and throughout the world.”
Addressing the Taoiseach directly, they say: “We offer our strong support to you in this effort.”
The only Democrat signatory is Dan Lipinski, from Chicago, who co-sponsored a bill to prevent women from obtaining abortions on health insurance unless they had been raped.