Citing concerns about her health, Aboriginal Affairs Minister John Duncan has urged Attiwapiskat Chief Theresa Spence to end her two week-long hunger strike.

In a letter sent Tuesday morning, Duncan reiterated an earlier offer to meet with Spence to discuss improving the treaty relationship between First Nations and the federal government.

Spence announced Dec. 11 that she would begin a hunger strike to bring attention to aboriginal rights. She has been living in a teepee on an island in the Ottawa River.

Spence is demanding a meeting with Prime Minister Stephen Harper, the governor general and First Nations leaders to discuss First Nations rights and treaties.

On Monday, Conservative Senator Patrick Brazeau attempted to meet with Spence but was turned down by her representatives.

Spence's hunger strike led to the national Idle No More movement, which in turn has spawned several protests and demonstrations.

First Nations leaders say they are concerned that the federal government is preparing to siphon power from band councils.

Activists are focused on the recently passed Bill C-45, the omnibus budget bill, that according to movement organizers will fast-track the process for aboriginals to surrender their reserve lands. Organizers also protest the new law because it includes clauses they say will slash the number of federally protected waterways and jeopardize lands they rely on. First Nations groups say they were not sufficiently consulted on the legislation.

An ongoing Sarnia, Ont., rail blockade created in protest of Bill C-45 and in support of Spence is now in its fifth day.

Staged by the Aamjiwnaang First Nation and their supporters, the blockade at the CN Rail line shuts off rail access to several chemical plants.

First Nations member Ron Plain said a representative for the rail company spoke with blockade organizers Monday, but nothing came of the talks. The First Nation contends that the tracks were not laid legitimately.

"Our view is a very solid view in that the tracks are not permitted on that road,” he said. “There was never any kind of permit issued for those tracks to cross there."

A court injunction has been issued to end the blockade, but Sarnia’s mayor has said police won’t interfere as long as the demonstration remains peaceful.

The group says it will not leave until Harper meets with Spence.

The Harper government, however, says it is taking the right steps to address First Nations’ rights.

The Dec. 25 letter to Spence noted the ministry was prepared to set a working group between federal and First Nations representatives to discuss treaty and right issues.

Meanwhile, members of First Nations groups near Sault Ste. Marie in northern Ontario have posted a message on Facebook indicating they are planning to launch a rail blockade on Thursday.

With files from The Canadian Press