In February 2016 ministers said funding would stay at £6.7m in 2016-17, whilst S4C's remit and funding was reviewed.
MPs urged ministers to drop plans to cut their contribution to £6.1m as the review had not yet begun.
Culture Minister Matt Hancock said secretary of state Karen Bradley was considering the matter. Most of S4C's £80m budget comes from the licence fee.
The Wales Office does not expect the investigation to be completed until the end of 2017.
During a Westminster debate on Wednesday, Mr Hancock said the Department of Culture, Media and Sport's contribution to S4C's budget was currently set to fall to £6.1m in 2017-18.
"We are aware of commitments given by our predecessor [ex-Culture Secretary John Whittingdale] around timing - and this is an issue the secretary of state [Karen Bradley] is currently considering," he said.
Ceredigion MP Mark Williams, who called the debate on S4C's future, said: "It is absolutely right that a review takes place to ensure that it has the funding necessary to fulfil its remit and strategy over the longer term.
"The comprehensive review into S4C announced in February last year, by the former secretary of state, along with a reversal of a cut, prior to the outcome of the review, was welcome.
"But we are now in 2017 and still waiting for a promised review, and there is cross-party concern about the delay."
Mr Hancock said there would be an announcement about the review "shortly" and promised that it would be chaired by someone with "a thorough understanding of Wales and an interest in the Welsh language".

Forward Fernando Forestieri (knee) is a doubt having only been able to play from the bench in the last two games.
Derby County striker David Nugent (groin) could return after missing Monday's draw with Huddersfield.
Midfielder Jacob Butterfield is hoping for a recall after coming off the bench to score a late leveller against the Terriers.

Mrs Schlafly was an outspoken opponent of feminism and abortion and helped Republicans block the Equal Rights Amendment in the 1970s.
She campaigned against Communism and is credited with creating the political climate that helped Ronald Reagan become president.
Mrs Schlafly publicly endorsed Donald Trump at a rally in March.
Paying tribute to her on Monday, the Republican presidential candidate described Mrs Schlafly as "a patriot, a champion for women and a symbol of strength".
Mrs Schlafly's death, in St Louis, was announced by the Eagle Forum, a conservative group she founded in 1972.
It described her as an "iconic  American leader whose love for America was surpassed only by her love of God and her family".
Mrs Schlafly was a strong advocate of traditional family values and one of her crowning political victories was helping to stop the Equal Rights Amendment [ERA] from being added to the US Constitution.
She once described feminists as "a bunch of bitter women seeking a constitutional cure for their personal problems".
Donald T Critchlow, author of a biography of Phyllis Schlafly, said that defeating the ERA helped to usher in a new conservative era in US politics, paving the way for Ronald Reagan's election in 1980.
The Eagle Forum said Mrs Schlafly was survived by her six children, 16 grandchildren and three great-grandchildren.
MPs have called on the UK government not to cut its funding of Welsh language channel S4C.
[NEXT_CONCEPT]
Sheffield Wednesday midfielder Kieran Lee (hip) could feature after three months out.
[NEXT_CONCEPT]
Phyllis Schlafly, a leading figure in the US conservative movement, has died at her home in Missouri, aged 92.